| 1. |
- Na Zhao, Li, et al.
(författare)
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Cascading proton transfers are a hallmark of the catalytic mechanism of SAM-dependent methyltransferases
- 2020
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 594:13, s. 2128-2139
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Tidskriftsartikel (refereegranskat)abstract
- The S-adenosyl-L-methionine (SAM)-dependent methyltransferases attach a methyl group to the deprotonated methyl lysine (Kme0) using SAM as a donor. An intriguing, yet unanswered, question is how the deprotonation of the methyl lysine takes place which results in a lone pair of electrons at the Nϵ atom of the methyl lysine for the following methyl transfer. PRDM9, one of the few methyltransferases with well-defined enzyme activity in vitro and in vivo, is a good representative of the PR/SET domain methyltransferase family to study the deprotonation and subsequently the methyl transfer. The reaction consists of two progressing steps: (i) the absolutely required substrate methyl lysine deprotonation and (ii) the transfer of the methyl group to the deprontonated methyl lysine. We use empirical valence bond (EVB) simulations to evaluate Y357 at the active site as potential general base for the deprotonation of the methyl lysine. Indeed, our study has found that the pKa of Tyr357 is low enough to make it an ideal candidate for proton abstraction from the methyl lysine. The partially deprontonated Tyr357 is able to change its H-bond pattern thus bridging two proton tunneling states (OH- H 0-Tyr357 and Kme0-Nϵ H O-Tyr357) and providing a cascading proton transfer from Tyr357 to hydroxide, generating deprotonated Tyr357 and then from Kme0 to the deprotonated Tyr357 resulting in deprotonated methyl lysine. This cascading proton transfer shortens the lifespan of the labile intermediates, and affects the conformational changes during the product release important to promote the proton release to the bulk solvent. Our computational efforts have uncovered a new catalytic mechanism to unravel the unanswered question about the deprotonation of the methyl lysine in methyltransferases.
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| 2. |
- Riesbeck, Kristian
(författare)
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Complement evasion by the human respiratory tract pathogens Haemophilus influenzae and Moraxella catarrhalis
- 2020
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 594:16, s. 2586-2597
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Forskningsöversikt (refereegranskat)abstract
- All infective bacterial species need to conquer the innate immune system in order to colonize and survive in their hosts. The human respiratory pathogens Haemophilus influenzae and Moraxella catarrhalis are no exceptions and have developed sophisticated mechanisms to evade complement-mediated killing. Both bacterial species carry lipooligosaccharides preventing complement attacks and attract and utilize host complement regulators C4b binding protein and factor H to inhibit the classical and alternative pathways of complement activation, respectively. In addition, the regulator of the terminal pathway of complement activation, vitronectin, is hijacked by both bacteria. An array of different outer membrane proteins (OMP) in H. influenzae and M. catarrhalis simultaneously binds complement regulators, but also plasminogen. Several of the bacterial complement-binding proteins are important adhesins and contain highly conserved regions for interactions with the host. Thus, some of the OMP are viable targets for new therapeutics, including vaccines aimed at preventing respiratory tract diseases such as otitis media in children and exacerbations in patients suffering from chronic obstructive pulmonary disease.
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| 3. |
- Ahmadpour, Doryaneh, 1973, et al.
(författare)
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The mitogen-activated protein kinase Slt2 modulates arsenite transport through the aquaglyceroporin Fps1
- 2016
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 590:20, s. 3649-3659
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Federation of European Biochemical Societies Arsenite is widely present in nature; therefore, cells have evolved mechanisms to prevent arsenite influx and promote efflux. In yeast (Saccharomyces cerevisiae), the aquaglyceroporin Fps1 mediates arsenite influx and efflux. The mitogen-activated protein kinase (MAPK) Hog1 has previously been shown to restrict arsenite influx through Fps1. In this study, we show that another MAPK, Slt2, is transiently phosphorylated in response to arsenite influx. Our findings indicate that the protein kinase activity of Slt2 is required for its role in arsenite tolerance. While Hog1 prevents arsenite influx via phosphorylation of T231 at the N-terminal domain of Fps1, Slt2 promotes arsenite efflux through phosphorylation of S537 at the C terminus. Our data suggest that Slt2 physically interacts with Fps1 and that this interaction depends on phosphorylation of S537. We hypothesize that Hog1 and Slt2 may affect each other's binding to Fps1, thereby controlling the opening and closing of the channel.
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| 4. |
- Birtele, Marcella, et al.
(författare)
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Dual modulation of neuron-specific microRNAs and the REST complex promotes functional maturation of human adult induced neurons
- 2019
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 593:23, s. 3370-3380
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Tidskriftsartikel (refereegranskat)abstract
- Direct neuronal reprogramming can be achieved using different approaches: by expressing neuronal transcription factors or microRNAs; and by knocking down neuronal repressive elements. However, there still exists a high variability in terms of the quality and maturity of the induced neurons obtained, depending on the reprogramming strategy employed. Here, we evaluate different long-term culture conditions and study the effect of expressing the neuronal-specific microRNAs, miR124 and miR9/9*, while reprogramming with forced expression of the transcription factors Ascl1, Brn2, and knockdown of the neuronal repressor REST. We show that the addition of microRNAs supports neuronal maturation in terms of gene and protein expression, as well as in terms of electrophysiological properties.
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| 5. |
- Daniel, Michael G., et al.
(författare)
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Induction of human hemogenesis in adult fibroblasts by defined factors and hematopoietic coculture
- 2019
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 593:23, s. 3266-3287
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Tidskriftsartikel (refereegranskat)abstract
- Transcription factor (TF)-based reprogramming of somatic tissues holds great promise for regenerative medicine. Previously, we demonstrated that the TFs GATA2, GFI1B, and FOS convert mouse and human fibroblasts to hemogenic endothelial-like precursors that generate hematopoietic stem progenitor (HSPC)-like cells over time. This conversion is lacking in robustness both in yield and biological function. Herein, we show that inclusion of GFI1 to the reprogramming cocktail significantly expands the HSPC-like population. AFT024 coculture imparts functional potential to these cells and allows quantification of stem cell frequency. Altogether, we demonstrate an improved human hemogenic induction protocol that could provide a valuable human in vitro model of hematopoiesis for disease modeling and a platform for cell-based therapeutics. Database: Gene expression data are available in the Gene Expression Omnibus (GEO) database under the accession number GSE130361.
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| 6. |
- Kelley, Liam P., et al.
(författare)
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Dimerization of small integral membrane protein 1 promotes cell surface presentation of the Vel blood group epitope
- 2020
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 594:8, s. 1261-1270
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Tidskriftsartikel (refereegranskat)abstract
- The Vel blood group antigen is carried on the short extracellular segment of the 78-amino-acid-long, type II transmembrane protein SMIM1 of unknown function. Here, using biochemical analysis and flow cytometry of cells expressing wild-type and mutant alleles of SMIM1, we demonstrate that dimerization of SMIM1 promotes cell surface display of the Vel epitope. We show that SMIM1 dimerization is mediated both by an extracellular Cys77-dependent, homomeric disulfide linkage and via a GxxxG helix–helix interaction motif in the transmembrane domain. These results provide important context for the observed variability in reactivity patterns of clinically important anti-Vel identified in patient sera.
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| 7. |
- Klaubauf, Sylvia, 1981, et al.
(författare)
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A novel L-arabinose-responsive regulator discovered in the rice-blast fungus Pyricularia oryzae (Magnaporthe oryzae)
- 2016
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 590:4, s. 550-558
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Tidskriftsartikel (refereegranskat)abstract
- In this study we identified the L-arabinose-responsive regulator of Pyricularia oryzae that regulates L-arabinose release and catabolism. Previously we identified the Zn2Cys6 transcription factor (TF), AraR, that has this role in the Trichocomaceae family (Eurotiales), but is absent in other fungi. Candidate Zn2Cys6 TF genes were selected according to their transcript profiles on L-arabinose. Deletion mutants of these genes were screened for their growth phenotype on L-arabinose. One mutant, named Delta ara1, was further analyzed. Our analysis demonstrated that Ara1 from P. oryzae is the functional analog of AraR from A. niger, while there is no significant sequence similarity between them.
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| 8. |
- Košenina, Sara, et al.
(författare)
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Crystal structure of the catalytic domain of the Weissella oryzae botulinum-like toxin
- 2019
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 593:12, s. 1403-1410
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Tidskriftsartikel (refereegranskat)abstract
- Botulinum neurotoxins (BoNTs) are the most potent toxins known. So far, eight serotypes have been identified that all act as zinc-dependent endopeptidases targeting SNARE proteins and inhibiting the release of neurotransmitters. Recently, the first botulinum toxin-like protein was identified outside the Clostridial genus, designated BoNT/Wo in the genome of Weissella oryzae. Here, we report the 1.6 angstrom X-ray crystal structure of the light chain of BoNT/Wo (LC/Wo). LC/Wo presents the core fold common to BoNTs but has an unusually wide, open and negatively charged catalytic pocket, with an additional Ca2+ ion besides the zinc ion and a unique ss-hairpin motif. The structural information will help establish the substrate profile of BoNT/Wo and help our understanding of how BoNT evolved.
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| 9. |
- Palmer, Nathan, et al.
(författare)
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Diverse roles for CDK-associated activity during spermatogenesis
- 2019
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 593:20, s. 2925-2949
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Forskningsöversikt (refereegranskat)abstract
- The primary function of cyclin-dependent kinases (CDKs) in complex with their activating cyclin partners, is to promote mitotic division in somatic cells. This canonical cell cycle-associated activity is also crucial for fertility as it allows the proliferation and differentiation of stem cells within the reproductive organs to generate meiotically competent cells. Intriguingly several CDKs exhibit meiosis-specific functions and are essential for the completion of the two reductional meiotic divisions required to generate haploid gametes. These meiosis-specific functions are mediated by both known CDK/cyclin complexes and meiosis-specific CDK-regulators and are important for a variety of processes during meiotic prophase. The majority of meiotic defects observed upon deletion of these proteins occur during the extended prophase I of the first meiotic division. Importantly a lack of redundancy is seen within the meiotic arrest phenotypes described for many of these proteins suggesting intricate layers of cell cycle control are required for normal meiotic progression. Using the process of male germ cell development (spermatogenesis) as a reference, this review seeks to highlight the diverse roles of selected CDKs their activators, and their regulators during gametogenesis.
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| 10. |
- Scaletti, Emma, et al.
(författare)
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Structural basis of inhibition of the human serine hydroxymethyltransferase SHMT2 by antifolate drugs
- 2019
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 593:14, s. 1863-1873
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Tidskriftsartikel (refereegranskat)abstract
- Serine hydroxymethyltransferase (SHMT) is the major source of 1-carbon units required for nucleotide synthesis. Humans have cytosolic (SHMT1) and mitochondrial (SHMT2) isoforms, which are upregulated in numerous cancers, making the enzyme an attractive drug target. Here, we show that the antifolates lometrexol and pemetrexed are inhibitors of SHMT2 and solve the first SHMT2-antifolate structures. The antifolates display large differences in their hydrogen bond networks despite their similarity. Lometrexol was found to be the best hSHMT1/2 inhibitor from a panel antifolates. Comparison of apo hSHMT1 with antifolate bound hSHMT2 indicates a highly conserved active site architecture. This structural information offers insights as to how these compounds could be improved to produce more potent and specific inhibitors of this emerging anti-cancer drug target.
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