| 1. |
- Ariöz, Candan, 1983-, et al.
(författare)
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Anionic Lipid Binding to the Foreign Protein MGS Provides a Tight Coupling between Phospholipid Synthesis and Protein Overexpression in Escherichia coli
- 2013
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 52:33, s. 5533-5544
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Tidskriftsartikel (refereegranskat)abstract
- Certain membrane proteins involved in lipid synthesis can induce formation of new intracellular membranes in Escherichia coli, i.e., intracellular vesicles. Among those, the foreign monotopic glycosyltransferase MGS from Acholeplasma laidlawii triggers such massive lipid synthesis when overexpressed. To examine the mechanism behind the increased lipid synthesis, we investigated the lipid binding properties of MGS in vivo together with the correlation between lipid synthesis and MGS overexpression levels. A good correlation between produced lipid quantities and overexpressed MGS protein was observed when standard LB medium was supplemented with four different lipid precursors that have significant roles in the lipid biosynthesis pathway. Interestingly, this correlation was highest concerning anionic lipid production and at the same time dependent on the selective binding of anionic lipid molecules by MGS. A selective interaction with anionic lipids was also observed in vitro by P-31 NMR binding studies using bicelles prepared with E. coli lipids. The results clearly demonstrate that the discriminative withdrawal of anionic lipids, especially phosphatidylglycerol, from the membrane through MGS binding triggers an in vivo signal for cells to create a feed-forward stimulation of lipid synthesis in E. coil. By this mechanism, cells can produce more membrane surface in order to accommodate excessively produced MGS molecules, which results in an interdependent cycle of lipid and MGS protein synthesis.
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| 2. |
- Babina, Arianne M., et al.
(författare)
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Rescue of Escherichia coli auxotrophy by de novo small proteins
- 2023
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Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Increasing numbers of small proteins with diverse physiological roles are being identified and characterized in both prokaryotic and eukaryotic systems, but the origins and evolution of these proteins remain unclear. Recent genomic sequence analyses in several organisms suggest that new functions encoded by small open reading frames (sORFs) may emerge de novo from noncoding sequences. However, experimental data demonstrating if and how randomly generated sORFs can confer beneficial effects to cells are limited. Here, we show that by upregulating hisB expression, de novo small proteins (<= 50 amino acids in length) selected from random sequence libraries can rescue Escherichia coli cells that lack the conditionally essential SerB enzyme. The recovered small proteins are hydrophobic and confer their rescue effect by binding to the 5 ' end regulatory region of the his operon mRNA, suggesting that protein binding promotes structural rearrangements of the RNA that allow increased hisB expression. This study adds RNA regulatory elements as another interacting partner for de novo proteins isolated from random sequence libraries and provides further experimental evidence that small proteins with selective benefits can originate from the expression of nonfunctional sequences.
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| 3. |
- Bai, Yang, et al.
(författare)
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Geometry design of tethered small-molecule acceptor enables highly stable and efficient polymer solar cells
- 2023
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- With the power conversion efficiency of binary polymer solar cells dramatically improved, the thermal stability of the small-molecule acceptors raised the main concerns on the device operating stability. Here, to address this issue, thiophene-dicarboxylate spacer tethered small-molecule acceptors are designed, and their molecular geometries are further regulated via the thiophene-core isomerism engineering, affording dimeric TDY-alpha with a 2, 5-substitution and TDY-beta with 3, 4-substitution on the core. It shows that TDY-alpha processes a higher glass transition temperature, better crystallinity relative to its individual small-molecule acceptor segment and isomeric counterpart of TDY-beta, and amore stablemorphology with the polymer donor. As a result, the TDY-alpha based device delivers a higher device efficiency of 18.1%, and most important, achieves an extrapolated lifetime of about 35000 hours that retaining 80% of their initial efficiency. Our result suggests that with proper geometry design, the tethered small-molecule acceptors can achieve both high device efficiency and operating stability.
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| 4. |
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| 5. |
- Brown, Christian, et al.
(författare)
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Structural and functional characterization of the microtubule interacting and trafficking domains of two oomycete chitin synthases
- 2016
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 283:16, s. 3072-3088
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Tidskriftsartikel (refereegranskat)abstract
- Chitin synthases (Chs) are responsible for the synthesis of chitin, a key structural cell wall polysaccharide in many organisms. They are essential for growth in certain oomycete species, some of which are pathogenic to diverse higher organisms. Recently, a Microtubule Interacting and Trafficking (MIT) domain, which is not found in any fungal Chs, has been identified in some oomycete Chs proteins. Based on experimental data relating to the binding specificity of other eukaryotic MIT domains, there was speculation that this domain may be involved in the intracellular trafficking of Chs proteins. However, there is currently no evidence for this or any other function for the MIT domain in these enzymes. To attempt to elucidate their function, MIT domains from two Chs enzymes from the oomycete Saprolegnia monoica were cloned, expressed and characterized. Both were shown to interact strongly with the plasma membrane component phosphatidic acid, and to have additional putative interactions with proteins thought to be involved in protein transport and localization. Aiding our understanding of these data, the structure of the first MIT domain from a carbohydrate-active enzyme (MIT1) was solved by NMR, and a model structure of a second MIT domain (MIT2) was built by homology modelling. Our results suggest a potential function for these MIT domains in the intracellular transport and/or regulation of Chs enzymes in the oomycetes.
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| 6. |
- Gustafsson, Robert, et al.
(författare)
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Structure and Characterization of Phosphoglucomutase 5 from Atlantic and Baltic Herring : An Inactive Enzyme with Intact Substrate Binding
- 2020
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Ingår i: Biomolecules. - : MDPI AG. - 2218-273X. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- Phosphoglucomutase 5 (PGM5) in humans is known as a structural muscle protein without enzymatic activity, but detailed understanding of its function is lacking. PGM5 belongs to the alpha-D-phosphohexomutase family and is closely related to the enzymatically active metabolic enzyme PGM1. In the Atlantic herring, Clupea harengus, PGM5 is one of the genes strongly associated with ecological adaptation to the brackish Baltic Sea. We here present the first crystal structures of PGM5, from the Atlantic and Baltic herring, diering by a single substitution Ala330Val. The structure of PGM5 is overall highly similar to structures of PGM1. The structure of the Baltic herring PGM5 in complex with the substrate glucose-1-phosphate shows conserved substrate binding and active site compared to human PGM1, but both PGM5 variants lack phosphoglucomutase activity under the tested conditions. Structure comparison and sequence analysis of PGM5 and PGM1 from fish and mammals suggest that the lacking enzymatic activity of PGM5 is related to dierences in active-site loops that are important for flipping of the reaction intermediate. The Ala330Val substitution does not alter structure or biophysical properties of PGM5 but, due to its surface-exposed location, could affect interactions with protein-binding partners.
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| 7. |
- Karlsson, Elin, 1992-, et al.
(författare)
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Intrinsically Disordered Flanking Regions Increase the Affinity of a Transcriptional Coactivator Interaction across Vertebrates
- 2023
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 62:18, s. 2710-2716
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between two proteins are often mediated by a disordered region in one protein binding to a groove in a folded interaction domain in the other one. While the main determinants of a certain interaction are typically found within a well-defined binding interface involving the groove, recent studies show that nonspecific contacts by flanking regions may increase the affinity. One example is the coupled binding and folding underlying the interaction between the two transcriptional coactivators NCOA3 (ACTR) and CBP, where the flanking regions of an intrinsically disordered region in human NCOA3 increases the affinity for CBP. However, it is not clear whether this flanking region-mediated effect is a peculiarity of this single protein interaction or if it is of functional relevance in a broader context. To further assess the role of flanking regions in the interaction between NCOA3 and CBP, we analyzed the interaction across orthologs and paralogs (NCOA1, 2, and 3) in human, zebra fish, and ghost shark. We found that flanking regions increased the affinity 2- to 9-fold in the six interactions tested. Conservation of the amino acid sequence is a strong indicator of function. Analogously, the observed conservation of increased affinity provided by flanking regions, accompanied by moderate sequence conservation, suggests that flanking regions may be under selection to promote the affinity between NCOA transcriptional coregulators and CBP.
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| 8. |
- Karlsson, Elin, et al.
(författare)
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Mapping the transition state for a binding reaction between ancient intrinsically disordered proteins
- 2020
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Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 295:51, s. 17698-17712
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Tidskriftsartikel (refereegranskat)abstract
- Intrinsically disordered protein domains often have multiple binding partners. It is plausible that the strength of pairing with specific partners evolves from an initial low affinity to a higher affinity. However, little is known about the molecular changes in the binding mechanism that would facilitate such a transition. We previously showed that the interaction between two intrinsically disordered domains, NCBD and CID, likely emerged in an ancestral deuterostome organism as a low-affinity interaction that subsequently evolved into a higher-affinity interaction before the radiation of modern vertebrate groups. Here we map native contacts in the transition states of the low-affinity ancestral and high-affinity human NCBD/CID interactions. We show that the coupled binding and folding mechanism is overall similar but with a higher degree of native hydrophobic contact formation in the transition state of the ancestral complex and more heterogeneous transient interactions, including electrostatic pairings, and an increased disorder for the human complex. Adaptation to new binding partners may be facilitated by this ability to exploit multiple alternative transient interactions while retaining the overall binding and folding pathway.
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| 9. |
- Kato, Norihiro, et al.
(författare)
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Trans-ancestry genome-wide association study identifies 12 genetic loci influencing blood pressure and implicates a role for DNA methylation
- 2015
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 47:11, s. 1282-1293
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Tidskriftsartikel (refereegranskat)abstract
- We carried out a trans-ancestry genome-wide association and replication study of blood pressure phenotypes among up to 320,251 individuals of East Asian, European and South Asian ancestry. We find genetic variants at 12 new loci to be associated with blood pressure (P = 3.9 × 10−11 to 5.0 × 10−21). The sentinel blood pressure SNPs are enriched for association with DNA methylation at multiple nearby CpG sites, suggesting that, at some of the loci identified, DNA methylation may lie on the regulatory pathway linking sequence variation to blood pressure. The sentinel SNPs at the 12 new loci point to genes involved in vascular smooth muscle (IGFBP3, KCNK3, PDE3A and PRDM6) and renal (ARHGAP24, OSR1, SLC22A7 and TBX2) function. The new and known genetic variants predict increased left ventricular mass, circulating levels of NT-proBNP, and cardiovascular and all-cause mortality (P = 0.04 to 8.6 × 10−6). Our results provide new evidence for the role of DNA methylation in blood pressure regulation.
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| 10. |
- Liebau, Jobst, et al.
(författare)
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Characterization of fast-tumbling isotropic bicelles by PFG diffusion NMR
- 2017
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 55:5, s. 395-404
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Forskningsöversikt (refereegranskat)abstract
- Small isotropic bicelles are versatile membrane mimetics, which, in contrast tomicelles, provide a lipid bilayer and are at the same time suitable for solution-state NMR studies. The lipid composition of the bilayer is flexible allowing for incorporation of various head groups and acyl chain types. In bicelles, lipids are solubilized by detergents, which are localized in the rimof the disk-shaped lipid bilayer. Bicelles have been characterized by a broad array of biophysical methods, pulsed-field gradient NMR (PFG NMR) being one of them. PFG NMR can readily be used to measure diffusion coefficients of macromolecules. It is thus employed to characterize bicelle size and morphology. Even more importantly, PFG NMR can be used to study the degree of protein association to membranes. Here, we present the advances that have been made in producing small, fast-tumbling isotropic bicelles from a variety of lipids and detergents, together with insights on the morphology of such mixtures gained from PFG NMR. Furthermore, we review approaches to study protein-membrane interaction by PFG NMR.
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| 11. |
- Lin, Xin (Maxwell), et al.
(författare)
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Smart coordinated multi-energy intra-scheduling inter-sharing and cost-saving redistribution for multiple microgrids
- 2023
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Ingår i: Sustainable cities and society. - : ELSEVIER. - 2210-6707. ; 97
-
Tidskriftsartikel (refereegranskat)abstract
- Sustainable and clean multi-energy systems have been hybrid coordinated in microgrid (MG) to fulfill regional multi-energy users economically, but shortages and surpluses still exist. The growth of win-win energy sharing between MGs attracts attention to smart information center (SIC) concept in MGs community, which facilitates sustainable solutions across three key objectives: lower carbon emission, sufficient utilization, and long-term cooperation. This paper designs a two-stage decision framework for day-ahead operations of SIC, where the first stage minimizes the total cost (i.e. operational cost and carbon emission cost) by the proposed multi-energy intra-scheduling and inter-sharing model (MIIM) and the second stage implements the smart cost-saving redistribution model (SCRM) to stimulate MGs in long-term joining of energy sharing. The extended alternating direction multipliers method algorithm (E-ADMM) is developed to protect the privacy of MGs data while approximating the optimal solution of MIIM. The case study proves that a) demand response and energy sharing in MIIM result in cost savings of 2.01% for carbon emissions and 7.25% for total operations; b) renewable energy has been fully utilized and the total multi-energy loss has been avoided nearly 92.22% in MIIM; c) the asymmetric Nash bargaining approach fits the SCRM with incentive cooperation, whereby those who contribute more gain a higher share; d) the optimal gap of E-ADMM is less than 0.2% by iterated insensitive decision result from each MG, which computes in polynomial time when the scale of MG increases; e) the two-stage framework performs better with more heterogeneity of MGs. Furthermore, we provide valuable insights for guidance and models with worldwide generalization potential.
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| 12. |
- Pettersson, Pontus, et al.
(författare)
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Structure and dynamics of plant TatA in micelles and lipid bilayers studied by solution NMR
- 2018
-
Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 285:10, s. 1886-1906
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Tidskriftsartikel (refereegranskat)abstract
- The twin-arginine translocase (Tat) transports folded proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. In Gram-negative bacteria and chloroplasts, the translocon consists of three subunits, TatA, TatB, and TatC, of which TatA is responsible for the actual membrane translocation of the substrate. Herein we report on the structure, dynamics, and lipid interactions of a fully functional C-terminally truncated core TatA' from Arabidopsisthaliana using solution-state NMR. Our results show that TatA consists of a short N-terminal transmembrane helix (TMH), a short connecting linker (hinge) and a long region with propensity to form an amphiphilic helix (APH). The dynamics of TatA were characterized using N-15 relaxation NMR in combination with model-free analysis. The TMH has order parameters characteristic of a well-structured helix, the hinge is somewhat less rigid, while the APH has lower order parameters indicating structural flexibility. The TMH is short with a surprisingly low protection from solvent, and only the first part of the APH is protected to some extent. In order to uncover possible differences in TatA's structure and dynamics in detergent compared to in a lipid bilayer, fast-tumbling bicelles and large unilamellar vesicles were used. Results indicate that the helicity of TatA increases in both the TMH and APH in the presence of lipids, and that the N-terminal part of the TMH is significantly more rigid. The results indicate that plant TatA has a significant structural plasticity and a capability to adapt to local environments.
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| 13. |
- Wu, Bo, et al.
(författare)
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Strong self-trapping by deformation potential limits photovoltaic performance in bismuth double perovskite
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Bismuth-based double perovskite Cs2AgBiBr6 is regarded as a potential candidate for low-toxicity, high-stability perovskite solar cells. However, its performance is far from satisfactory. Albeit being an indirect bandgap semiconductor, we observe bright emission with large bimolecular recombination coefficient (reaching 4.5 +/- 0.1 x 10(-11) cm(3) s(-1)) and low charge carrier mobility (around 0.05 cm(2) s(-1) V-1). Besides intermediate Frohlich couplings present in both Pb-based perovskites and Cs2AgBiBr6, we uncover evidence of strong deformation potential by acoustic phonons in the latter through transient reflection, time-resolved terahertz measurements, and density functional theory calculations. The Frohlich and deformation potentials synergistically lead to ultrafast self-trapping of free carriers forming polarons highly localized on a few units of the lattice within a few picoseconds, which also breaks down the electronic band picture, leading to efficient radiative recombination. The strong self-trapping in Cs2AgBiBr6 could impose intrinsic limitations for its application in photovoltaics.
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| 14. |
- Ye, Weihua, 1983-
(författare)
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Biophysical studies of membrane associated biomolecular interactions
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Membrane associated interactions play important roles in various biological processes. The aim of this thesis is to study two types of membrane associated interactions by using biophysical methods, particularly NMR. First, the interaction of a targeting peptide and a receptor attached to membrane has been studied. Secondly, we were interested in the interaction between a galactosyltransferase and the involved membrane lipids, galactolipids, and thus novel membrane mimetic models containing galactolipids have been studied. In addition, membrane mimetic models, bicelles, under different conditions have been characterized. The targeting peptide studied here is a dual targeting peptide, ThrRS-dTP(2-60), which is capable of targeting a t-RNA synthase, ThrRS, to both the mitochondrial matrix and the chloroplast stroma. Tom20 is the first component in the mitochondrial outer membrane import machinary that interacts with ThrRS-dTP(2-60). Biophysical studies in this thesis on the dTP-Tom20 interaction showed that it shares several features with the interaction between mitochondrial targeting peptides and Tom20. An amphiphilic helix with a fccff motif from ThrRS-dTP(2-60) is crucial for the interaction with Tom20 and more than one region was involved. However, a relatively long C-terminal part of the peptide was not affected by the interaction with Tom20. Novel membrane mimetic media were developed by introducing the galactolipids MGDG and DGDG into DMPC/DHPC bicelles. Diffusion NMR results indicated that there is no phase separation upon incorporation of as much as 30% galactoplids. The sizes of the new bicelles were, however, larger than DMPC/DHPC bicelles. 13C relaxation measurements showed that galactolipids in the bicelles have two distinct local dynamic regions: the galactose units together with the glycerol linker region, with limited local motion, and the acyl chains with extensive motion. The bicelles with galactolipids are suitable for studies of e.g. the interaction between the galactosyltransferases and galactolipids. Additionally, studies on the morphology of DMPC/DHPC mixtures under various conditions were performed. The size distribution for small, fast-tumbing bicelles was observed to be dependent on the q-value (the mole ratio between the long-chained lipids and the short-chained lipids), temperature and the total lipid concentration. With larger q-values and low concentrations, the DMPC/DHPC mixture was not monodisperse, as additional structures were observed in both dynamic light scattering and cryogenic transmission electron microscopy experiments. Hence, care is needed when using bicelles under new conditions.
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| 15. |
- Ye, Weihua, et al.
(författare)
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Characterization of the Morphology of Fast-Tumbling Bicelles with Varying Composition
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:19, s. 5488-5496
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Tidskriftsartikel (refereegranskat)abstract
- Small, fast-tumbling bicelles are frequently used in solution NMR studies of protein lipid interactions. For this purpose it is critical to have information about the organization of the lipids within the bicelle structure. We have studied the morphology of small, fast-tumbling bicelles containing DMPC and DHPC as a function of temperature, lipid concentration, and the relative ratio (q value) of lipid (DMPC) to detergent (DHPC) amounts. Dynamic light scattering and cryo-transmission electron microscopy techniques were used to measure the size of the bicelles and to monitor the shape and dispersity of the particles in the samples. The stability and size of DMPC-containing bicelle mixtures were found to be highly dependent on temperature and the total lipid concentration for mixtures with q = 1 and q = 1.5. Stable DMPC/DHPC bicelles are only formed at low q values (0.5). Bicelle mixtures with q > 0.5 appear to be multidisperse containing more than one component, one with r(H) around 2.5 nm and one with r(H) of 6-8 nm. This is interpreted as a coexistence of small (possibly mixed micelles) bicelles and much larger bicelles. Incubating the sample at 37 degrees C increases the phase separation. Moreover, low total amphiphile concentrations and low q values lead to the formation of a temperature-independent morphology, interpreted as the formation of small particles in which the DHPC and DMPC are more mixed. On the basis of these results, we propose the existence of a critical bicelle concentration, a parameter that determines the existence of bilayered bicelles, which varies with q value. This polymorphism was not observed at any concentrations for q = 0.5 bicelles, for which a small but detectable temperature dependence was observed at high concentrations. The results demonstrate that q = 0.5 mixtures predominantly form classical bicelles, but that caution is needed when using fast-tumbling mixtures with q values higher than 0.5.
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| 16. |
- Ye, Weihua, et al.
(författare)
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Folded Alpha Helical Putative New Proteins from Apilactobacillus kunkeei
- 2024
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Ingår i: Journal of Molecular Biology. - : Elsevier. - 0022-2836 .- 1089-8638. ; 436:6
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of new proteins is a central question in biology. Most tertiary protein folds known to date appear to have an ancient origin, but it is clear from bioinformatic analyses that new proteins continuously emerge in all organismal groups. However, there is a paucity of experimental data on new proteins regarding their structure and biophysical properties. We performed a detailed phylogenetic analysis and identified 48 putative open reading frames in the honeybee -associated bacterium Apilactobacillus kunkeei for which no or few homologs could be identified in closely -related species, suggesting that they could be relatively new on an evolutionary time scale and represent recently evolved proteins. Using circular dichroism-, fluorescence- and nuclear magnetic resonance (NMR) spectroscopy we investigated six of these proteins and show that they are not intrinsically disordered, but populate alpha -helical dominated folded states with relatively low thermodynamic stability (0-3 kcal/mol). The NMR and biophysical data demonstrate that small new proteins readily adopt simple folded conformations suggesting that more complex tertiary structures can be continuously re -invented during evolution by fusion of such simple secondary structure elements. These findings have implications for the general view on protein evolution, where de novo emergence of folded proteins may be a common event.
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| 17. |
- Ye, Weihua, et al.
(författare)
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Interaction of the dual targeting peptide of Thr-tRNA synthetase with the chloroplastic receptor Toc34 in Arabidopsis thaliana
- 2015
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Ingår i: FEBS Open Bio. - : Wiley. - 2211-5463. ; 5, s. 405-412
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Tidskriftsartikel (refereegranskat)abstract
- Organellar proteins synthesized in the cytosol are usually selective for only one destination in a cell but some proteins are localized in more than one compartment, for example in both mitochondria and chloroplasts. The mechanism of dual targeting of proteins to mitochondria and chloroplasts is yet poorly understood. Previously, we observed that the dual targeting peptide of threonyl-tRNA synthetase in Arabidopsis thaliana (AtThrRS-dTP) interacts with the mitochondrial receptor AtTom20 mainly through its N-terminal part. Here we report on the interaction of AtThrRS-dTP with the chloroplastic receptor AtToc34, presenting for the first time the mode of interactions of a dual targeting peptide with both Tom20 and Toc34. By NMR spectroscopy we investigated changes in (15)(N) HSQC spectra of AtThrRS-dTP as a function of AtToc34 concentration. Line broadening shows that the interaction with AtToc34 involves residues along the entire sequence, which is not the case for AtTom20. The N-terminal phi chi chi phi phi motif, which plays an important role in AtTom20 recognition, shows no specificity for AtToc34. These results are supported by import competition studies into both mitochondria and chloroplasts, in which the effect of peptides corresponding to different segments of AtThrRS-dTP on in vitro import of organelle specific proteins was examined. This demonstrates that the N-terminal A2-Y29 segment of AtThrRS-dTP is essential for import into both organelles, while the C-terminal L30-P60 part is important for chloroplastic import efficiency. In conclusion, we have demonstrated that the recognition of the dual targeting peptide of AtThr-tRNA synthetase is different for the mitochondrial and chloroplastic receptors. (C) 2015 The Authors. Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies. This is an open access article under the CC BY-NC-ND license.
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| 18. |
- Ye, Weihua, et al.
(författare)
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New Membrane Mimetics with Galactolipids : Lipid Properties in Fast-Tumbling Bicelles
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 117:4, s. 1044-1050
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Tidskriftsartikel (refereegranskat)abstract
- Galactolipids are the main structural component of plant chloroplastic (thylakoid) membranes and of blue-green algae cell membranes. The predominant lipids in this class are monogalactosyl-diacylglycerol (MGDG) and digalactosyl-diacylglycerol (DGDG). We here present a method for the preparation of bicelles that contain these galactolipids together with a characterization of the bicelles, and the lipids within the bicelles. NMR diffusion data show that up to 3096 of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in a q = 0.5 DMPC/DHPC lipid matrix can be replaced with either monogalactosyl-diacylglycerol or digalactosyl-diacylglycerol and that these lipids incorporate into the bicelles. No evidence for phase separation is observed. Bicelles made with monogalactosyl-diacylglycerol are significantly larger than bicelles containing only DMPC, already with only 1096 of the DMPC replaced with the galactolipid. The effect of digalactosyl-diacylglycerol on bicelle size is much smaller. These observations are likely to be correlated with the different bilayer-forming properties of the lipids. Monogalactosyl-diacylglycerol is a non-bilayer-forming lipid, while digalactosyl-diacylglycerol is a bilayer-forming lipid. Both galactolipids display extensive local motion within the bilayer, as evidenced by natural abundance carbon-13 relaxation of the lipid molecules. The sugar headgroup regions are motionally restricted and cannot be described by a model that does not take into account anisotropic reorientation of the sugar units. No significant effect of the galactolipids on DMPC dynamics was observed. Our results indicate that these bicelles may become useful as model membrane mimetic media for studies of galactolipid-protein interactions.
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| 19. |
- Ye, Weihua, et al.
(författare)
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NMR investigations of the dual targeting peptide of Thr-tRNA synthetase and its interaction with the mitochondrial Tom20 receptor in Arabidopsis thaliana
- 2012
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 279:19, s. 3738-3748
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Tidskriftsartikel (refereegranskat)abstract
- Most mitochondrial proteins are synthesized in the cytosol as precursor proteins containing an N-terminal targeting peptide and are imported into mitochondria through the import machineries, the translocase of the outer mitochondrial membrane (TOM) and the translocase of the inner mitochondrial membrane (TIM). The N-terminal targeting peptide of precursor proteins destined for the mitochondrial matrix is recognized by the Tom20 receptor and plays an important role in the import process. Protein import is usually organelle specific, but several plant proteins are dually targeted into mitochondria and chloroplasts using an ambiguous dual targeting peptide. We present NMR studies of the dual targeting peptide of Thr-tRNA synthetase and its interaction with Tom20 in Arabidopsis thaliana. Our findings show that the targeting peptide is mostly unstructured in buffer, with a propensity to form a-helical structure in one region, S6F27, and a very weak beta-strand propensity for Q34Q38. The a-helical structured region has an amphiphilic character and a f??ff motif, both of which have previously been shown to be important for mitochondrial import. Using NMR we have mapped out two regions in the peptide that are important for Tom20 recognition: one of them, F9V28, overlaps with the amphiphilic region, and the other comprises residues L30Q39. Our results show that the targeting peptide may interact with Tom20 in several ways. Furthermore, our results indicate a weak, dynamic interaction. The results provide for the first time molecular details on the interaction of the Tom20 receptor with a dual targeting peptide. Database The backbone chemical shift assignments for ThrRS-dTP(260) have been deposited with the Biological Magnetic Resonance Bank (BMRB) under the accession code 18248 Structured digital abstract ThrRS-dTP and Tom20-4 bind by nuclear magnetic resonance (View interaction)
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| 20. |
- Ye, Weihua, 1983-
(författare)
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One key to two doors : Dual targeting peptides and membrane mimetics
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A targeting peptide at the N-terminus of a precursor protein usually directs the protein synthesized in the cytosol to a specific organelle in the cell. Interestingly, some targeting peptides, so-called dual targeting peptides (dTPs) can target their protein to both mitochondria and chloroplasts. In order to understand the mechanism of dual targeting, a dTP from threonyl tRNA synthetase (ThrRS-dTP) was investigated as a model dTP in this thesis work. The results suggest that ThrRS-dTP is intrinsically disordered in solution but has an α-helical propensity at the N-terminal part. Tom20 and Toc34 are the two primary receptors on the outer membranes of mitochondria and chloroplasts, respectively. We found that the N-terminal half of the ThrRS-dTP sequence, including an amphiphilic helix, is important for the interaction with Tom20. This part also contains a φχχφφ motif, where φ represents a hydrophobic/aromatic residue and χ represents any amino acid residue. In contrast, neither the amphiphilic helix nor φχχφφ motif in ThrRS-dTP has any special role for its interaction with Toc34. Instead, the entire sequence of ThrRS-dTP is important for Toc34 interaction, including the C-terminal part which is barely affected by Tom20 interaction.In addition, the role of lipids in the organelle membrane for the recognition of dual targeting peptides during protein import is also the focus of this thesis. The tendency to form α-helix in ThrRS-dTP, which is not observable in solution by CD, becomes obvious in the presence of lipids and DPC micelles. To be able to study such interactions, DMPC/DHPC isotropic bicelles under different conditions have also been characterized. These results demonstrate that bicelles with a long-chained/short-chained lipid ratio q = 0.5 and a concentration larger than 75 mM should be used to ensure that the classic bicelle morphology persists. Moreover, we developed a novel membrane mimetic system containing the galactolipids, MGDG or DGDG, which have been proposed to be important for protein import into chloroplasts. Up to 30% MGDG or DGDG lipids were able to be integrated into bicelles. The local dynamics of the galactolipids in bicelles displays two types of behavior: the sugar head-group and the glycerol part are rigid, and the acyl chains are flexible.
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