| 1. |
- Aboye, Teshome L., et al.
(författare)
-
A Cactus-Derived Toxin-Like Cystine Knot Peptide with Selective Antimicrobial Activity
- 2015
-
Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 16:7, s. 1068-1077
-
Tidskriftsartikel (refereegranskat)abstract
- Naturally occurring cystine knot peptides show a wide range of biological activity, and as they have inherent stability they represent potential scaffolds for peptide-based drug design and biomolecular engineering. Here we report the discovery, sequencing, chemical synthesis, three-dimensional solution structure determination and bioactivity of the first cystine knot peptide from Cactaceae (cactus) family: Ep-AMP1 from Echinopsis pachanoi. The structure of Ep-AMP1 (35 amino acids) conforms to that of the inhibitor cystine knot (or knottin) family but represents a novel diverse sequence; its activity was more than 500 times higher against bacterial than against eukaryotic cells. Rapid bactericidal action and liposome leakage implicate membrane permeabilisation as the mechanism of action. Sequence homology places Ec-AMP1 in the plant C6-type of antimicrobial peptides, but the three dimensional structure is highly similar to that of a spider neurotoxin.
|
|
| 2. |
|
|
| 3. |
- Boldbaatar, Delgerbat, et al.
(författare)
-
Synthesis, Structural Characterization, and Bioactivity of the Stable Peptide RCB-1 from Ricinus communis
- 2015
-
Ingår i: Journal of natural products (Print). - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 78:11, s. 2545-2551
-
Tidskriftsartikel (refereegranskat)abstract
- The Ricinus communis biomarker peptides RCB-1 to -3 comprise homologous sequences of 19 (RCB-1) or 18 (RCB-2 and -3) amino acid residues. They all include four cysteine moieties, which form two disulfide bonds. However, neither the 3D structure nor the biological activity of any of these peptides is known. The synthesis of RCB-1, using microwave-assisted, Fmoc-based solid-phase peptide synthesis, and a method for its oxidative folding are reported. The tertiary structure of RCB-1, subsequently established using solution-state NMR, reveals a twisted loop fold with antiparallel ?-sheets reinforced by the two disulfide bonds. Moreover, RCB-1 was tested for antibacterial, antifungal, and cytotoxic activity, as well as in a serum stability assay, in which it proved to be remarkably stable.
|
|
| 4. |
- Burman, Robert, et al.
(författare)
-
Chemistry and Biology of Cyclotides : Circular Plant Peptides Outside the Box
- 2014
-
Ingår i: Journal of natural products (Print). - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 77:3, s. 724-736
-
Forskningsöversikt (refereegranskat)abstract
- Cyclotides stand out as the largest family of circular proteins of plant origin hitherto known, with more than 280 sequences isolated at peptide level and many more predicted from gene sequences. Their unusual stability resulting from the signature cyclic cystine knot (CCK) motif has triggered a broad interest in these molecules for potential therapeutic and agricultural applications. Since the time of the first cyclotide discovery, our laboratory in Uppsala has been engaged in cyclotide discovery as well as the development of protocols to isolate and characterize these seamless peptides. We have also developed methods to chemically synthesize cyclotides by Fmoc-SPPS, which are useful in protein grafting applications. In this review, experience in cyclotide research over two decades and the recent literature related to their structures, synthesis, and folding as well the recent proof-of-concept findings on their use as "epitope" stabilizing scaffolds are summarized.
|
|
| 5. |
- Cárdenas, Paco, 1976-, et al.
(författare)
-
Good Practices in Sponge Natural Product Studies : Revising Vouchers with Isomalabaricane Triterpenes
- 2022
-
Ingår i: Marine Drugs. - : MDPI. - 1660-3397. ; 20:3
-
Tidskriftsartikel (refereegranskat)abstract
- Species misidentification in the field of natural products is an acknowledged problem. These errors are especially widespread in sponge studies, albeit rarely assessed and documented. As a case study, we aim to revisit reports of isomalabaricane triterpenes, isolated from four demosponge genera: Jaspis, Geodia, Stelletta and Rhabdastrella. From a total of 44 articles (1981-2022), 27 unique vouchers were listed, 21 of which were accessed and re-examined here: 11 (52.4%) of these were misidentified. Overall, 65.9% of the studies published an incorrect species name: previously identified Jaspis and Stelletta species were all in fact Rhabdastrella globostellata. We conclude that isomalabaricane triterpenes were isolated from only two Rhabdastrella species and possibly one Geodia species. In addition to shedding a new light on the distribution of isomalabaricane triterpenes, this study is an opportunity to highlight the crucial importance of vouchers in natural product studies. Doing so, we discuss the impact of species misidentification and poor accessibility of vouchers in the field of sponge natural products. We advocate for stricter voucher guidelines in natural product journals and propose a common protocol of good practice, in the hope of reducing misidentifications in sponge studies, ensure reproducibility of studies, and facilitate follow-up work on the original material.
|
|
| 6. |
- Carstens, Bodil B., et al.
(författare)
-
Isolation, characterization, and synthesis of the Barrettides : disulfide-containing peptides from the marine sponge Geodia barretti
- 2015
-
Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 78:8, s. 1886-1893
-
Tidskriftsartikel (refereegranskat)abstract
- Two disulfide-containing peptides, barrettides A (1) and B (2), from the cold-water marine sponge Geodia barretti are described. Those 31 amino acid residue long peptides were sequenced using mass spectrometry methods and structurally characterized using NMR spectroscopy. The structure of 1 was confirmed by total synthesis using the solid-phase peptide synthesis approach that was developed. The two peptides were found to differ only at a single position in their sequence. The three-dimensional structure of 1 revealed that these peptides possess a unique fold consisting of a long β-hairpin structure that is cross-braced by two disulfide bonds in a ladder-like arrangement. The peptides are amphipathic in nature with the hydrophobic and charged residues clustered on separate faces of the molecule. The barrettides were found not to inhibit the growth of either Escherichia coli or Staphylococcus aureus but displayed antifouling activity against barnacle larvae (Balanus improvisus) without lethal effects in the concentrations tested. (Figure Presented).
|
|
| 7. |
|
|
| 8. |
- Eriksson, Camilla, 1986-
(författare)
-
Cyclic peptides as biological tools : Applications for diagnosis and therapeutics in rheumatoid arthritis and COVID-19
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aims of the projects included in this thesis were to design, synthesize and evaluate cyclic peptide scaffolds grafted with biological epitopes for their ability to bind antibodies in rheumatoid arthritis and COVID-19 sera. One of the main outcomes of this thesis was the observation that scaffold peptides grafted with target epitopes efficiently neutralized anti-citrullinated protein autoantibodies (ACPA) from rheumatoid arthritis patients. Another main outcome was that grafted cyclic scaffold peptides demonstrated potential for use in COVID-19 diagnostics.In paper I and II, peptides grafted with epitopes from reported ACPA target proteins were designed, synthesized and evaluated for ACPA-neutralizing activity. Cyclic scaffold peptides and linear peptides were compared. In paper I, we demonstrate that the peptides based on the stable scaffold sunflower trypsin inhibitor-1 (SFTI-1) can be used to neutralize ACPA. The peptides s[Cit-Fil](306-323), s[Cit-Vim](60-75) and s[Cit-Vim](2-17) were particularly efficient, and blocked 80-93% with IC50-values ranging from 5.6 -82 µM. Moreover we show that compared to their linear counterparts, these peptides demonstrated enhanced stability in human serum.In paper II, scaffold peptides from the PDP-family (PawS-derived peptides) with different structural properties were evaluated for ACPA-neutralizing activity. By grafting the same ACPA target epitope on three PDP-peptides, their impact on antibody binding could be compared to the linear epitope and to an SFTI-grafted epitope. No substantial difference in antibody binding was contributed by the scaffolds, but a reduction in background was observed for the PDP-peptides when compared to the SFTI-1-peptide. The peptides demonstrated enhanced serum stability in vitro.In Paper III, grafted SFTI-1-scaffold peptides were applied to COVID-19 antibody detection. SFTI-1 was grafted with immunodominant epitopes from SARS-CoV-2 virus spike protein. Epitopes in linear form were synthesized for comparison. A SARS-CoV-2 ELISA was developed and a cohort of positive and negative samples were tested for anti-SARS-CoV-2 reactivity. The peptide (S2_1146-1161_c) stood out as a promising antigen and recognized positive and negative sera with similar capacity as both a lateral flow test and a commercial SARS-CoV-2 ELISA. In paper IV, cyclic scaffold peptides grafted with epitopes from SARS-CoV-2 proved useful in an antibody proximity extension assay, both at detecting and distinguishing COVID-19 positive and negative sera.
|
|
| 9. |
- Eriksson, Camilla, et al.
(författare)
-
Epitopes displayed in a cyclic peptide scaffold bind SARS-CoV-2 antibodies
- 2023
-
Ingår i: ChemBioChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4227 .- 1439-7633. ; 24:15
-
Tidskriftsartikel (refereegranskat)abstract
- The SARS-CoV-2 virus that causes COVID-19 is a global health issue. The spread of the virus has resulted in seven million deaths to date. The emergence of new viral strains highlights the importance of continuous surveillance of the SARS-CoV-2 virus by using timely and accurate diagnostic tools. Here, we used a stable cyclic peptide scaffolds to present antigenic sequences derived from the spike protein that are reactive to SARS-CoV-2 antibodies. Using peptide sequences from different domains of SARS-CoV-2 spike proteins, we grafted epitopes on the peptide scaffold sunflower trypsin inhibitor 1 (SFTI-1). These scaffold peptides were then used to develop an ELISA to detect SARS-CoV-2 antibodies in serum. We show that displaying epitopes on the scaffold improves reactivity overall. One of the scaffold peptides (S2_1146-1161_c) has reactivity equal to that of commercial assays, and shows diagnostic potential.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Fernandes-Cerqueira, Catia, et al.
(författare)
-
Targeting of anti-citrullinated protein/peptide antibodies in rheumatoid arthritis using peptides mimicking endogenously citrullinated fibrinogen antigens
- 2015
-
Ingår i: Arthritis Research & Therapy. - : Springer Science and Business Media LLC. - 1478-6362 .- 1478-6354. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: We have previously identified endogenously citrullinated peptides derived from fibrinogen in rheumatoid arthritis (RA) synovial tissues. In this study, we have investigated the auto-antigenicity of four of those citrullinated peptides, and explored their feasibility to target anti-citrullinated protein/peptide antibodies (ACPA). Methods: The autoantigenic potential of the fibrinogen peptides was investigated by screening 927 serum samples from the Epidemiological Investigation of RA (EIRA) cohort on a peptide microarray based on the ImmunoCAP ISAC (R) system. In order to assay for ACPA blocking, two independent pools of purified ACPA were incubated with the respective targeting peptide prior to binding to cyclic citrullinated peptide (CCP) 2 using the CCPlus (R) ELISA kit. Results: Two peptides derived from the fibrinogen a chain, Arg573Cit (563-583) and Arg591Cit (580-600), referred to as Cit573 and Cit591, and two peptides from the fibrinogen beta chain, Arg72Cit (62-81) and Arg74Cit (62-81) (Cit72 and Cit74), displayed 65 %, 15 %, 35 %, and 53 % of immune reactivity among CCP2-positive RA sera, respectively. In CCP2-negative RA sera, a positive reactivity was detected in 5 % (Cit573), 6 % (Cit591), 8 % (Cit72), and 4 % (Cit74). In the competition assay, Cit573 and Cit591 peptides reduced ACPA binding to CCP2 by a maximum of 84 % and 63 % respectively. An additive effect was observed when these peptides were combined. In contrast, Cit74 and Cit72 were less effective. Cyclization of the peptide structure containing Cit573 significantly increased the blocking efficiency. Conclusions: Here we demonstrate extensive autoantibody reactivity against in vivo citrullinated fibrinogen epitopes, and further show the potential use of these peptides for antagonizing ACPA.
|
|
| 13. |
- Gunasekera, Sunithi, 1977-, et al.
(författare)
-
Alanine and Lysine Scans of the LL-37-Derived Peptide Fragment KR-12 Reveal Key Residues for Antimicrobial Activity
- 2018
-
Ingår i: ChemBioChem. - : WILEY-V C H VERLAG GMBH. - 1439-4227 .- 1439-7633. ; 19:9, s. 931-939
-
Tidskriftsartikel (refereegranskat)abstract
- The human host defence peptide LL-37 is a broad-spectrum antibiotic with immunomodulatory functions. Residues 18-29 in LL-37 have previously been identified as a minimal peptide (KR-12) that retains antibacterial activity with decreased cytotoxicity. In this study, analogues of KR-12 were generated by Ala and Lys scans to identify key elements for activity. These were tested against a panel of human pathogens and for membrane permeabilisation on liposomes. Replacements of hydrophobic and cationic residues with Ala were detrimental for antibiotic potency. Substitutions by Lys increased activity, as long as the increase in cationic density did not disrupt the amphiphilic disposition of the helical structure. Importantly, substitutions showed differential effects against different organisms. Replacement of Gln5 with Lys and Asp9 with Ala or Lys improved the broad-spectrum activity most, each resulting in up to an eightfold increase in potency against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. The improved analogues displayed no significant toxicity against human cells, and thus, KR-12 is a tuneable template for antibiotic development.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Gunasekera, Sunithi, 1977-, et al.
(författare)
-
Backbone Cyclization and Dimerization of LL-37-Derived Peptides Enhance Antimicrobial Activity and Proteolytic Stability
- 2020
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; :11
-
Tidskriftsartikel (refereegranskat)abstract
- Can antimicrobial activity and peptide stability of alpha-helical peptides be increased by making them into dimers and macrocycles? Here, we explore that concept by using KR-12 as the starting point for peptide engineering. KR-12 has previously been determined as the minimalized antimicrobial fragment of the human host defense peptide LL-37. Backbone-cyclized KR-12 dimers, tethered by linkers of two to four amino acid residues, were synthesized and their antimicrobial activity, proteolytic stability and structures characterized. A modified KR-12 sequence, with substitutions at previously identified key residues, were also included in the screening panel. The backbone cyclized KR-12 dimers showed improved antimicrobial activity and increased stability compared to monomeric KR-12. The most active cyclic dimer displayed 16-fold higher antibacterial activity compared to KR-12 against Pseudomonas aeruginosa and Staphylococcus aureus, and 8-fold increased fungicidal activity against Candida albicans. It also showed increased hemolytic and cytotoxic activity. Enhanced antimicrobial activity coincided with increased membrane permeabilization of liposomes with one distinct discrepancy: monomeric KR-12 was much less disruptive of liposomes with bacterial lipid composition compared to liposomes from fungal lipid extract. Circular dichroism showed that the four-residue linked most active cyclic dimer had 65% helical content when bound to lyso-phosphatidylglycerol micelles, indicating that the helical propensity of the parent peptide is maintained in the new macrocyclic form. In conclusion, the current work on KR-12 suggests that dimerization together with backbone cyclization is an effective strategy for improving both potency and stability of linear antimicrobial peptides.
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Gunasekera, Sunithi, et al.
(författare)
-
Fmoc-SPPS based synthesis of bioactive cyclic peptides via N-acylurea intermediates
- 2012
-
Ingår i: Journal of Peptide Science. - : Wiley. - 1075-2617 .- 1099-1387. ; 18:suppl 1, s. S182-S182
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The plant cyclotides form the largest family of cyclic peptides(1). They contain a signature motif referred to as the cyclic cystine knot, which is derived from the cyclic backbone and three inter-knotted disulfide bonds. Intriguingly, cyclotides can be boiled, treated with chemicals or enzymes without disrupting their overall fold. Thus, they are sometimes labeled as ultra-stable proteins. In addition, cyclotides are tolerant to mutations, and as a scaffold they can successfully accommodate foreign bioactive epitopes of variable sequences(2). Cyclotides share many of these properties with another disulfide containing cyclic plant peptide, the sunflower trypsin inhibitor 1 (SFTI-1)(3). Emerging evidence indicates that cyclotides and SFTI-1 are valuable not only as peptide stabilizing scaffolds; in combination with their cell penetrating properties, these disulfide rich cyclic peptides have significance as intracellular drug carriers. Although both peptides are genetically encoded, studies to ascertain the exact mechanisms of their biosynthesis are currently on going. Thus, the synthesis of cyclotides and SFTI-1 are currently restricted to chemical means. We have recently adapted a Fmoc-SPPS method for cyclic peptide synthesis, via N-acylurea intermediates with the assistance of microwave irradiation.This method is a safe and convenient alternative to Boc-SPPS and has the ability to be automated conveniently. Using this method, parent scaffolds as well as several cyclotide and SFTI-1 analogues with potential antimicrobial and matrix metalloprotease activities were synthesized. With the rising interest in the cyclization concept as a tool to impart stability on unstable peptides, the cyclic peptide synthesis method adapted herein is anticipated to have numerous applications.1. Burman, R.; Gunasekera, S.; Stromstedt, A.; Rosengren, J.; Goransson, U. J. Biol. Chem. 2012 (in press)2. Gunasekera, S.; Foley, F. M.; Clark, R. J.; Sando, L.; Fabri, L. J.; Craik, D. J.; Daly, N. L. J. Med. Chem. 2008, 51, 7697.3. Chan, L. Y.; Gunasekera, S.; Henriques, S. T.; Worth, N. F.; Le, S. J.; Clark, R. J.; Campbell, J. H.; Craik, D. J.; Daly, N. L. Blood 2011, 118, 6709.
|
|
| 20. |
- Gunasekera, Sunithi, et al.
(författare)
-
Making Ends Meet : Microwave-Accelerated Synthesis of Cyclic and Disulfide Rich Proteins Via In Situ Thioesterification and Native Chemical Ligation
- 2013
-
Ingår i: International Journal of Peptide Research and Therapeutics. - : Springer Science and Business Media LLC. - 1573-3149 .- 1573-3904. ; 19:1- SI, s. 43-54
-
Tidskriftsartikel (refereegranskat)abstract
- The development of synthetic methodologies for cyclic peptides is driven by the discovery of cyclic peptide drug scaffolds such as the plant-derived cyclotides, sunflower trypsin inhibitor 1 (SFTI-1) and the development of cyclized conotoxins. Currently, the native chemical ligation reaction between an N-terminal cysteine and C-terminal thioester group remains the most robust method to obtain a head-to-tail cyclized peptide. Peptidyl thioesters are effectively generated by Boc SPPS. However, their generation is challenging using Fmoc SPPS because thioester linkers are not stable to repeated piperidine exposure during deprotection. Herein we describe a Fmoc-based protocol for synthesizing cyclic peptides adapted for microwave assisted solid phase peptide synthesis. The protocol relies on the linker Di-Fmoc-3,4-diaminobenzoic acid, and we demonstrate the use of Gly, Ser, Arg and Ile as C-terminal amino acids (using HBTU and HATU as coupling reagents). Following synthesis, an N-acylurea moiety is generated at the C-terminal of the peptide; the resin bound acylurea peptide is then deprotected and cleaved from the resin. The fully deprotected peptide undergoes thiolysis in aqueous buffer, generating the thioester in situ. Ultimately, the head-to-tail cyclized peptide is obtained via native chemical ligation. Two naturally occurring cyclic peptides, the prototypical Mobius cyclotide kalata B1 and SFTI-1 were synthesized efficiently, avoiding potential branching at the diamino linker, using the optimized protocol. In addition, we demonstrate the possibility to use the approach for the synthesis of long and synthetically challenging linear sequences, by the ligation of two truncated fragments of a 50-residue long plant defensin.
|
|
| 21. |
- Gunasekera, Sunithi, 1977-, et al.
(författare)
-
Stabilized Cyclic Peptides as Scavengers of Autoantibodies : Neutralization of Anticitrullinated Protein/Peptide Antibodies in Rheumatoid Arthritis
- 2018
-
Ingår i: ACS Chemical Biology. - : American Chemical Society (ACS). - 1554-8929 .- 1554-8937. ; 13:6, s. 1525-1535
-
Tidskriftsartikel (refereegranskat)abstract
- The occurrence of autoantibodies is a hallmark of rheumatoid arthritis, specifically those autoantibodies targeting proteins containing the arginine-derived amino acid citrulline. There is strong evidence showing that the occurrence of anticitrullinated protein/peptide antibodies (ACPA) are involved in disease progression, and ACPA was recently shown to induce pain in animals. Here, we explore a novel concept useful for research, diagnostics, and possibly therapy of autoimmune diseases, namely, to directly target and neutralize autoantibodies using peptide binders. A high-affinity peptide-based scavenger of ACPA was developed by grafting a citrullinated epitope derived from human fibrinogen into a naturally occurring stable peptide scaffold. The best scavenger comprises the truncated epitope α-fibrinogen, [Cit573]fib(566-580), grafted into the scaffold sunflower trypsin inhibitor-1, SFTI-1. The final peptide demonstrates low nanomolar apparent affinity and superior stability.
|
|
| 22. |
- Gunasekera, Sunithi, et al.
(författare)
-
Strategies for macrocyclic cyclotide synthesis
- 2010
-
Ingår i: Posters 001-067: Synthetic Chemistry of Amino Acids and Peptides. - : Wiley. ; , s. 65-65
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 23. |
- Göransson, Ulf, et al.
(författare)
-
Circular Proteins from Plants and Fungi
- 2012
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 287:32, s. 27001-27006
-
Forskningsöversikt (refereegranskat)abstract
- Circular proteins, defined as head-to-tail cyclized polypeptides originating from ribosomal synthesis, represent a novel class of natural products attracting increasing interest. From a scientific point of view, these compounds raise questions of where and why they occur in nature and how they are formed. From a rational point of view, these proteins and their structural concept may be exploited for crop protection and novel pharmaceuticals. Here, we review the current knowledge of three protein families: cyclotides and circular sunflower trypsin inhibitors from the kingdom of plants and the Amanita toxins from fungi. A particular emphasis is placed on their biological origin, structure, and activity. In addition, the opportunity for discovery of novel circular proteins and recent insights into their mechanism of action are discussed.
|
|
| 24. |
|
|
| 25. |
- Hellinger, Roland, et al.
(författare)
-
Chemical Proteomics for Target Discovery of Head-to-Tail Cyclized Mini-Proteins
- 2017
-
Ingår i: Frontiers in Chemistry. - : FRONTIERS MEDIA SA. - 2296-2646. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Target deconvolution is one of the most challenging tasks in drug discovery, but a key step in drug development. In contrast to small molecules, there is a lack of validated and robust methodologies for target elucidation of peptides. In particular, it is difficult to apply these methods to cyclic and cysteine-stabilized peptides since they exhibit reduced amenability to chemical modification and affinity capture; however, such ribosomally synthesized and post-translationally modified peptide natural products are rich sources of promising drug candidates. For example, plant-derived circular peptides called cyclotides have recently attracted much attention due to their immunosuppressive effects and oral activity in the treatment of multiple sclerosis in mice, but their molecular target has hitherto not been reported. In this study, a chemical proteomics approach using photo-affinity crosslinking was developed to determine a target for the circular peptide [T20K]kalata B1. Using this prototypic nature-derived peptide enabled the identification of a possible functional modulation of 14-3-3 proteins. This biochemical interaction was validated via competition pull down assays as well as a cellular reporter assay indicating an effect on 14-3-3-dependent transcriptional activity. As proof of concept, the presented approach may be applicable for target elucidation of various cyclic peptides and mini-proteins, in particular cyclotides, which represent a promising class of molecules in drug discovery and development.
|
|
| 26. |
|
|
| 27. |
- Koehbach, Johannes, et al.
(författare)
-
Oxytocic plant cyclotides as templates for peptide G protein-coupled receptor ligand design
- 2013
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:52, s. 21183-21188
-
Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are plant peptides comprising a circular backbone and three conserved disulfide bonds that confer them with exceptional stability. They were originally discovered in Oldenlandia affinis based on their use in traditional African medicine to accelerate labor. Recently, cyclotides have been identified in numerous plant species of the coffee, violet, cucurbit, pea, potato, and grass families. Their unique structural topology, high stability, and tolerance to sequence variation make them promising templates for the development of peptide-based pharmaceuticals. However, the mechanisms underlying their biological activities remain largely unknown; specifically, a receptor for a native cyclotide has not been reported hitherto. Using bioactivity-guided fractionation of an herbal peptide extract known to indigenous healers as "kalata-kalata," the cyclotide kalata B7 was found to induce strong contractility on human uterine smooth muscle cells. Radioligand displacement and second messenger-based reporter assays confirmed the oxytocin and vasopressin V-1a receptors, members of the G protein-coupled receptor family, as molecular targets for this cyclotide. Furthermore, we show that cyclotides can serve as templates for the design of selective G protein-coupled receptor ligands by generating an oxytocin-like peptide with nanomolar affinity. This nonapeptide elicited dose-dependent contractions on human myometrium. These observations provide a proof of concept for the development of cyclotide-based peptide ligands.
|
|
| 28. |
|
|
| 29. |
- Kosgahakumbura, Lakmini, et al.
(författare)
-
Screening for antibacterial and cytotoxic activities of Sri Lankan marine sponges through microfractionation : Isolation of bromopyrrole alkaloids from Stylissa massa
- 2024
-
Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 19:1
-
Tidskriftsartikel (refereegranskat)abstract
- Sri Lanka is a biodiversity hotspot and one of the richest geographical locations of marine sponges in the Indian ocean. However, the most extensive taxonomical study on Sri Lankan sponge biodiversity dates back similar to 100 years and only a limited number of studies have been conducted on sponge natural products. In the current study, 35 marine sponge specimens (collected from 16 sponge habitats around Sri Lanka) were identified, microfractionated and evaluated for antibacterial and anticancer assays. In total, 30 species were characterized, of which 19 species gave extracts with antibacterial and/or cytotoxic activities. Microfractionated organic extract of Aciculites orientalis gave the most potent antibacterial activity against Staphylococcus aureus and strongest lymphoma cell toxicity was exhibited by the organic extract of Acanthella sp. Guided by the molecular ion peaks in the bioactive fractions, large-scale extraction of Stylissa massa led to the isolation of three bromopyrrole alkaloids, sceptrin, hymenin and manzacidin A/C. Of these, sceptrin exhibited broad spectrum antibacterial activity against both Escherichia coli and S. aureus (MIC of 62.5 mu M against both species). Based on natural product literature, seven promising species were identified as understudied. Their further exploration may lead to the discovery of structurally novel compounds.
|
|
| 30. |
|
|
| 31. |
- Mohotti, Supun, et al.
(författare)
-
Screening for bioactive secondary metabolites in Sri Lankan medicinal plants by microfractionation and targeted isolation of antimicrobial flavonoids from Derris scandens
- 2020
-
Ingår i: Journal of Ethnopharmacology. - : Elsevier BV. - 0378-8741 .- 1872-7573. ; 246
-
Tidskriftsartikel (refereegranskat)abstract
- Ethnopharmacological relevance: Sri Lanka is known to have very diverse flora. Many of these species are used for plant-based remedies, which form the integral part of two Sri Lankan systems of traditional medicine, Ayurveda and Deshiya Chikitsa. Despite their widespread use, only a limited number of studies have probed into the scientific evidence for bioactivity of these medicinal plants. Such studies rarely progress to the identification of bioactive natural products. Aim of the study: The primary aim was to develop a bioactivity screening method and apply it to 50 Sri Lankan medicinal plants where antimicrobial properties could be relevant for its traditional use. The subsequent aim was the progression into defining and characterising potent isolates within targeted compound classes from such plants, i.e. Derris scandens and its antimicrobial flavonoids. Material and methods: The plant collection comprised 24 species of Fabaceae, 15 Rubiaceae, 7 Solanaceae and 4 Cucurbitaceae plants. These 50 species were collected based on their ethnopharmacological importance and use in Sri Lankan traditional medicine. Crude extracts from each species were initially subjected to radial disc diffusion and microdilution assays. Subsequently, aqueous extracts of all plants were microfractionated in deep well plates using reversed-phase HPLC. Fractions were tested for antibacterial and cytotoxic activities and masses of target bioactive compounds were identified using mass spectrometry. Bioactive compounds with the masses identified through microfractions were isolated from Derris scandens using reversed-phase HPLC. The isolated pure compounds were characterised using LC-MS and NMR. Results: Crude aqueous extracts from 19 species showed activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) in the radial disc diffusion assay. Crude aqueous extracts from 34 plant species and organic extracts from 46 plant species were active against S. aureus (<= 4 mg mL(-1)) in the microdilution assay. Microfractionation demonstrated antibacterial activity for 19 plants and cytotoxicity for 6 plants. Furthermore, target bioactive compounds and their molecular ions were identified during microfractionation. Dalpanitin and vicenin-3, two of the flavonoids isolated from Derris scandens gave MICs of 23 mu g mL(-1) against S. aureus. Dalpanitin also exhibited relevant MICs on Gram-negative bacteria (94 mu g mL(-1)) against Escherichia coli and Pseudomonas aeruginosa). Conclusion: The microfractionation protocol developed in this study enabled time-efficient screening of many plants species, using a small quantity of sample material. In addition, microfractionation served as a guiding tool for identifying individual antimicrobial compounds. Through this process, flavonoids were isolated from Derris scandens, out of which dalpanitin and vicenin-3 showed activity in the low micromolar range. The high hit rate for in vitro antibacterial properties from this ethnopharmacologically guided sample collection gives credence to Sri Lankan traditional herbal medicine as a source for drug discovery.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Muhammad, Taj, et al.
(författare)
-
Exploring the limits of cyanobactin macrocyclase PatGmac : Cyclization of PawS-derived peptide sunflower trypsin inhibitor-1 and cyclotide kalata B1
- 2023
-
Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0974-5211 .- 0163-3864 .- 1520-6025. ; 86:3, s. 566-573
-
Tidskriftsartikel (refereegranskat)abstract
- The subtilisin-like macrocyclase PatGmac is produced by the marine cyanobacterium Prochloron didemni. This enzyme is involved in the last step of the biosynthesis of patellamides, a cyanobactin type of ribosomally expressed and post-translationally modified cyclic peptides. PatGmac recognizes, cleaves, and cyclizes precursor peptides after a specific recognition motif comprised of a C-terminal tail with the sequence motif -AYDG. The result is the native macrocyclic patellamide, which has eight amino acid residues. Macrocyclase activity can be exploited by incorporating that motif in other short linear peptide precursors, which then are formed into head-to-tail cyclized peptides. Here, we explore the possibility of using PatGmac in the cyclization of peptides larger than the patellamides, namely, the PawS-derived peptide sunflower trypsin inhibitor-1 (SFTI-1) and the cyclotide kalata B1. These peptides fall under two distinct families of disulfide constrained macrocyclic plant peptides. They are both implicated as scaffolds for drug design due to their structures and unusual stability. We show that PatGmac can be used to efficiently cyclize the 14 amino acid residue long SFTI-1, but less so the 29 amino acid residue long kalata B1.
|
|
| 35. |
|
|
| 36. |
- Muhammad, Taj, 1982-
(författare)
-
LL-37-derived cyclic antimicrobial drug leads : Design, synthesis, activity and different ways of creating them
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In an era where last-line antibiotics are failing, one of the powerful approaches to develop novel therapeutic agents is to turn back to nature in order to identify possible drug candidates. Among the potential candidates, antimicrobial peptides (AMPs) have garnered much attention as an antimicrobial. These are broad spectrum host defense molecules produced by all living organisms. LL-37 is such a multitask human defense peptide that mediates various host immune responses and also exerts antimicrobial activity. However, the direct use of this 37-amino acid long α-helical peptide is hampered by protease susceptibility, in particular for antimicrobial applications. A small 12-residues peptide, referred as KR-12, derived from LL-37, has been reported to have selective toxic effect on bacteria. Analogues of KR-12 were generated in the form of Alanine and Lysine scans to find out the positions important for improved activity and selectivity. Backbone-cyclised dimers based on KR-12 and KR-12 analogues, tethered by linkers of two to four amino acid residues, were synthesised to explore the concept of cyclisation, dimerisation and cross-linking as means to enhance peptide stability and activity. Antimicrobial activities of the linear peptides and cyclic dimers were assayed against human pathogens, in buffer and/or physiological conditions. Proteolytic stability, permeabilisation efficacy on microbial membranes and, their structures were also characterised. From Ala and Lys scans, it was possible to identify two key positions for the enhanced broad-spectrum antibacterial activity: replacement of Gln5 with Lys, and Asp9 with either Ala or Lys. In serum stability assay, KR-12 and analogues were found to be unstable. The backbone-cyclised KR-12 dimers showed improved antimicrobial activity and increased stability compared to monomeric KR-12. KR-12 monomers adopt a well-defined α-helical structure in membrane-mimicking environment, while cyclised dimers were unstructured in solution judged by NMR. The KR-12 (Q5K, D9A) cyclised dimers retained antimicrobial activity in physiological conditions. Circular dichroism showed that the cyclic dimer, cd4-PP, had 77% helical content when bound to lyso-phosphatidylglycerol micelles.Moreover, the limits of cyanobactin-macrocyclase PatGmac were explored to cyclise peptides larger than their natural substrates, namely the PawS derived peptide Sunflower Trypsin Inhibitor-1 (SFTI-1) and the cyclotide kalata B1. PatGmac was used very efficiently to cyclise SFTI-1. In addition, semi-pure butelase 1, isolated from Clitoria ternatea seeds, was immobilised on NHS column. The immobilised column was then used to produce substrates ranging from 16 to 34 varying length.
|
|
| 37. |
|
|
| 38. |
- Muhammad, Taj, et al.
(författare)
-
Transforming Cross-Linked Cyclic Dimers of KR-12 into Stable and Potent Antimicrobial Drug Leads
- 2023
-
Ingår i: Biomedicines. - : MDPI. - 2227-9059. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- Is it possible to enhance structural stability and biological activity of KR-12, a truncated antimicrobial peptide derived from the human host defense peptide LL-37? Based on the mapping of essential residues in KR-12, we have designed backbone-cyclized dimers, cross-linked via a disulfide bond to improve peptide stability, while at the same time improving on-target activity. Circular dichroism showed that each of the dimers adopts a primarily alpha-helical conformation (55% helical content) when bound to lyso-phosphatidylglycerol micelles, indicating that the helical propensity of the parent peptide is maintained in the new cross-linked cyclic form. Compared to KR-12, one of the cross-linked dimers showed 16-fold more potent antimicrobial activity against human pathogens Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans and 8-fold increased activity against Escherichia coli. Furthermore, these peptides retained antimicrobial activity at physiologically relevant conditions, including in the presence of salts and in human serum, and with selective Gram-negative antibacterial activity in rich growth media. In addition to giving further insight into the structure-activity relationship of KR-12, the current work demonstrates that by combining peptide stabilization strategies (dimerization, backbone cyclization, and cross-linking via a disulfide bond), KR-12 can be engineered into a potent antimicrobial peptide drug lead with potential utility in a therapeutic context.
|
|
| 39. |
- Park, Sungkyu, et al.
(författare)
-
An Efficient Approach for the Total Synthesis of Cyclotides by Microwave Assisted Fmoc-SPPS
- 2010
-
Ingår i: International Journal of Peptide Research and Therapeutics. - : Springer Science and Business Media LLC. - 1573-3149 .- 1573-3904. ; 16:3, s. 167-176
-
Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are mini-proteins of approximately 30 amino acid residues that have a unique structure consisting of a head-to-tail cyclized backbone and a knotted arrangement of three disulfide bonds. This unique cyclotide structure provides exceptional stability to chemical, enzymatic and thermal treatments and has been implicated as an ideal drug scaffold for the development into agricultural and biotechnological agents. In the current work, we present the first method for microwave assisted Fmoc-SPPS of cyclotides. This protocol adopts a strategy that combines optimized microwave assisted chemical reactions for Fmoc-SPPS of the peptide backbone, the cleavage of the protected peptide and the introduction of a thioester at the C-terminal carboxylic acid to obtain the head-to-tail cyclized cyclotide backbone by native chemical ligation. To exemplify the utility of this protocol in the synthesis of a wide array of different cyclotide sequences we synthesized representative members from the three cyclotide subfamilies-the Mobius kalata B1, the bracelet cycloviolacin O2 and the trypsin inhibitory MCoTI-II. In addition, a "one pot" reaction promoting both cyclization and oxidative folding of crude peptide thioester was adapted for kalata B1 and MCoTI-II.
|
|
| 40. |
- Park, SungKyu, et al.
(författare)
-
Microwave-assisted total synthesis of macrocyclic cystine knot miniproteins
- 2010
-
Ingår i: Journal of Peptide Science. - : Wiley. - 1075-2617 .- 1099-1387. ; 16:S1, s. 79-79
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Microwave-assisted total synthesis of macrocyclic cystine knot miniproteins SK Park, S Gunasekera, T Aboye, U Göransson Division of pharmacognosy, Uppsala university, UPPSALA, Sweden Cyclotides are mini-proteins of approximately 30 amino acids residues that have a unique structure consisting of a head-to-tail cyclic backbone with a knotted arrangement of three disulfide bonds [1]. This unique structure provides exceptional stability to chemical, enzymatic and thermal treatments [2,3]. Cyclotides display various bioactivities, such as anti-HIV, uterotonic, cytotoxic, and insecticidal activity [4]. Due to the unique structural stability, cyclotides have been implicated as ideal drug scaffolds and for development into agricultural and biotechnological agents [2]. In the current work, we represent the first method for total synthesis of cyclotides based on Fmoc-SPPS assisted by microwave. This protocol adopts a strategy that combines the optimized microwave assisted chemical reactions for Fmoc-SPPS of peptide backbone synthesis, thioesterification of the C-terminal carboxylic acid of the peptide and a one pot reaction that promotes cyclisation through native chemical ligation and oxidative folding. The application of this protocol was exemplified for the synthesis of two prototypic cyclotides; kalata B1 and MCOTI-II
|
|
| 41. |
- Rajendran, Sanjeevan, et al.
(författare)
-
Antibacterial eremophilane sesquiterpenoids from Xylaria feejeensis, an endophytic fungi of the medicinal plant Geophila repens
- 2023
-
Ingår i: Fitoterapia. - : Elsevier. - 0367-326X .- 1873-6971. ; 167
-
Tidskriftsartikel (refereegranskat)abstract
- Geophila repens (L.) I.M. Johnst (Rubiaceae) is a traditional medicinal plant used in Sri Lanka for the treatment of bacterial infections. Due to its rich endophytic fungi content, it was postulated that endophytically-produced specialized metabolites may be responsible for its purported antibacterial effects. To test this hypothesis, eight pure endophytic fungal cultures were isolated from G. repens then extracted and screened for antibacterial activity in a disc diffusion assay against Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. Large scale culturing, extraction, and purification of the most active fungal extract, obtained from Xylaria feejeensis, led to the isolation of 6′,7′-didehydrointegric acid (1), 13-carboxyintegric acid (2), and four known compounds including integric acid (3). Compound 3 was isolated as the key antibacterial component (MIC = 16 μg/mL against Bacillus subtilis, 64 μg/mL against Methicillin-Resistant S. aureus). Compound 3 and its analogues were devoid of hemolytic activity up to the highest tested concentration of 45 μg/mL. This study demonstrates that specialized metabolites produced by endophytic fungi may contribute to the biological activity of some medicinal plants. Endophytic fungi should be evaluated as a potential source of antibiotics, especially from unexplored medicinal plants traditionally used for the treatment of bacterial infections.
|
|
| 42. |
- Rajendran, Sanjeevan, et al.
(författare)
-
Screening for Cyclotides in Sri Lankan Medicinal Plants : Discovery, Characterization, and Bioactivity Screening of Cyclotides from Geophila repens
- 2023
-
Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 86:1, s. 52-65
-
Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are an intriguing class of structurally stable circular miniproteins of plant origin with numerous potential pharmaceutical and agricultural applications. To investigate the occurrence of cyclotides in Sri Lankan flora, 50 medicinal plants were screened, leading to the identification of a suite of new cyclotides from Geophila repens of the family Rubiaceae. Cycloviolacin O2-like (cyO2-like) gere 1 and the known cyclotide kalata B7 (kB7) were among the cyclotides characterized at the peptide and/or transcript level together with several putative enzymes, likely involved in cyclotide biosynthesis. Five of the most abundant cyclotides were isolated, sequenced, structurally characterized, and screened in antimicrobial and cytotoxicity assays. All gere cyclotides showed cytotoxicity (IC50 of 2.0-10.2 mu M), but only gere 1 inhibited standard microbial strains at a minimum inhibitory concentration of 4-16 mu M. As shown by immunohistochemistry, large quantities of the cyclotides were localized in the epidermis of the leaves and petioles of G. repens. Taken together with the cytotoxicity and membrane permeabilizing activities, this implicates gere cyclotides as potential plant defense molecules. The presence of cyO2-like gere 1 in a plant in the Rubiaceae supports the notion that phylogenetically distant plants may have coevolved to express similar cytotoxic cyclotides for a specific functional role, most likely involving host defense.
|
|
| 43. |
- Rajendran, Sanjeevan, et al.
(författare)
-
Tropical vibes from Sri Lanka - cyclotides from Viola betonicifolia by transcriptome and mass spectrometry analysis
- 2021
-
Ingår i: Phytochemistry. - : Elsevier. - 0031-9422 .- 1873-3700. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are an extremely stable class of peptides, ubiquitously distributed in Violaceae. The aim of the present study was to investigate the presence of cyclotides in Sri Lankan Violaceae plants, using combined tools of transcriptomics and mass spectrometry. New cyclotides were discovered for the first time in the wild flora of Sri Lanka, within Viola betonicifolia, a plant used in traditional medicine as an antimicrobial. Plant extracts prepared in small scale from Viola betonicifolia were first subjected to LC-MS analysis. Subsequent transcriptome de novo sequencing of Viola betonicifolia uncovered 25 new (vibe 1-25) and three known (varv A/kalata S, viba 17, viba 11) peptide sequences from Mobius and bracelet cyclotide subfamilies as well as hybrid cyclotides. Among the transcripts, putative linear acyclotide sequences (vibe 4, vibe 10, vibe 11 and vibe 22) that lack a conserved asparagine or aspartic acid vital for cyclisation were also present. Four asparagine endopeptidases (AEPs), VbAEP1-4 were found within the Viola betonicifolia transcriptome, including a peptide asparaginyl ligase (PAL), potentially involved in cyclotide backbone cyclisation, showing >93% sequence homology to Viola yedoensis peptide asparaginyl ligases, VyPALs. In addition, we identified two protein disulfide isomerases (PDIs), VbPDI1-2, likely involved in cyclotide oxidative folding, having high sequence homology (>74%) with previously reported Rubiaceae and Violaceae PDIs. The current study highlights the ubiquity of cyclotides in Violaceae as well as the utility of transcriptomic analysis for cyclotides and their putative processing enzyme discovery. The high variability of cyclotide sequences in terms of loop sizes and residues in V. betonicifolia showcase the cyclotide structure as an adaptable scaffold as well as their importance as a combinatorial library, implicated in plant defense.
|
|
| 44. |
- Steffen, Karin, 1989-, et al.
(författare)
-
Barrettides : A Peptide Family Specifically Produced by the Deep-Sea Sponge Geodia barretti
- 2021
-
Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 84:12, s. 3138-3146
-
Tidskriftsartikel (refereegranskat)abstract
- Natural product discovery by isolation and structure elucidation is a laborious task often requiring ample quantities of biological starting material and frequently resulting in the rediscovery of previously known compounds. However, peptides are a compound class amenable to an alternative genomic, transcriptomic, and in silico discovery route by similarity searches of known peptide sequences against sequencing data. Based on the sequences of barrettides A and B, we identified five new barrettide sequences (barrettides C-G) predicted from the North Atlantic deep-sea demosponge Geodia barretti (Geodiidae). We synthesized, folded, and investigated one of the newly described barrettides, barrettide C (NVVPCFCVEDETSGAKTCIPDNCDASRGTNP, disulfide connectivity I-IV, II-III). Co-elution experiments of synthetic and sponge-derived barrettide C confirmed its native conformation. NMR spectroscopy and the anti-biofouling activity on larval settlement of the bay barnacle Amphibalanus improvisus (IC50 0.64 μM) show that barrettide C is highly similar to barrettides A and B in both structure and function. Several lines of evidence suggest that barrettides are produced by the sponge itself and not one of its microbial symbionts.
|
|
| 45. |
- Strömstedt, Adam A., et al.
(författare)
-
Selective membrane disruption by the cyclotide kalata B7: complex ions and essential functional groups in the phosphatidylethanolamine binding pocket
- 2016
-
Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434 .- 0005-2736. ; 1858:6, s. 1317-1327
-
Tidskriftsartikel (refereegranskat)abstract
- The cyclic cystine knot plant peptides called cyclotides are active against a wide variety of organisms. This is primarily achieved through membrane binding and disruption, in part deriving from a high affinity for phosphatidylethanolamine (PE) lipids. Some cyclotides, such as kalata B7 (kB7), form complexes with divalent cations in a pocket associated with the tyrosine residue at position 15 (Tyr15). In the current work we explore the effect of cations on membrane leakage caused by cyclotides kB1, kB2 and kB7, and we identify a functional group that is essential for PE selectivity. The presence of PE-lipids in liposomes increased the membrane permeabilizing potency of the cyclotides, with the potency of kB7 increasing by as much as 740-fold. The divalent cations Mn(2+), Mg(2+) and Ca(2+) had no apparent effect on PE selectivity. However, amino acid substitutions in kB7 proved that Tyr15 is crucial for PE-selective membrane permeabilization on various liposome systems. Although the tertiary structure of kB7 was maintained, as reflected by the NMR solution structure, mutating Tyr into Ser at position 15 resulted in substantially reduced PE selectivity. Ala substitution at the same position produced a similar reduction in PE selectivity, while substitution with Phe maintained high selectivity. We conclude that the phenyl ring in Tyr15 is critical for the high PE selectivity of kB7. Our results suggest that PE-binding and divalent cation coordination occur in the same pocket without adverse effects of competitive binding for the phospholipid.
|
|
| 46. |
- Svangård, Erika, et al.
(författare)
-
Mechanism of action of cytotoxic cyclotides : cycloviolacin O2 disrupts lipid membranes
- 2007
-
Ingår i: Journal of natural products (Print). - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 70:4, s. 643-647
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, the cyclotides have emerged as the largest family of naturally cyclized proteins. Cyclotides display potent cytotoxic activity that varies with the structure of the proteins, and combined with their unique structure, they represent novel cytotoxic agents. However, their mechanism of action is yet unknown. In this work we show that disruption of cell membranes plays a crucial role in the cytotoxic effect of the cyclotide cycloviolacin O2 (1), which has been isolated from Viola odorata. Cell viability and morphology studies on the human lymphoma cell line U-937 GTB showed that cells exposed to 1 displayed disintegrated cell membranes within 5 min. Functional studies on calcein-loaded HeLa cells and on liposomes showed rapid concentration-dependent release of their respective internal contents. The present results show that cyclotides have specific membrane-disrupting activity.
|
|
| 47. |
|
|
| 48. |
- White, John Kerr, et al.
(författare)
-
A stable cyclized antimicrobial peptide derived from LL-37 with host immunomodulatory effects and activity against uropathogens
- 2022
-
Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Nature. - 1420-682X .- 1420-9071. ; 79:8
-
Tidskriftsartikel (refereegranskat)abstract
- The increasing antibiotic resistance among uropathogenic bacteria warrants alternative therapeutic strategies. We demonstrate the potential of the synthetic peptide CD4-PP, designed by dimerization and backbone cyclization of the shortest antimicrobial region of human cathelicidin, LL-37. CD4-PP is active against clinical and type strains of common uropathogens Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa at concentrations substantially below cellular cytotoxic levels and induced membrane deformation and leakage in E. coli and P. aeruginosa. Furthermore, CD4-PP treatment prevented the formation of new biofilm and dissolved mature biofilm created by E. coli and P. aeruginosa and targeted curli amyloid in E. coli biofilms. In addition, CD4-PP also induced production of LL-37 by uroepithelial cells and increased the expression of tight junction proteins claudin-14 and occludin. During uroepithelial cell infection, CD4-PP significantly reduced uropathogen survival when treatment was given at the start of infection. Low micromolar of CD4-PP treatment initiated after 2 h was successful with all tested species, except P. aeruginosa where CD4-PP was unable to reduce survival, which could be attributed by early biofilm formation. Finally, we demonstrated that urinary catheter pieces coated with saline fluid supplemented with CD4-PP reduced the attachment of E. coli, giving it a potential clinical application.
|
|
| 49. |
|
|
| 50. |
- Zumberge, J. Alex, et al.
(författare)
-
Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals
- 2018
-
Ingår i: Nature Ecology & Evolution. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 2:11, s. 1709-1714
-
Tidskriftsartikel (refereegranskat)abstract
- Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100 Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C-30 sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.
|
|
