201
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The topogenic function of S4 promotes membrane insertion of the voltage-sensor domain in the KvAP channel. Biochem J 2016; 473:4361-4372. [PMID: 27694387 DOI: 10.1042/bcj20160746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 09/20/2016] [Accepted: 09/30/2016] [Indexed: 11/17/2022]
Abstract
Voltage-dependent K+ (KV) channels control K+ permeability in response to shifts in the membrane potential. Voltage sensing in KV channels is mediated by the positively charged transmembrane domain S4. The best-characterized KV channel, KvAP, lacks the distinct hydrophilic region corresponding to the S3-S4 extracellular loop that is found in other K+ channels. In the present study, we evaluated the topogenic properties of the transmembrane regions within the voltage-sensing domain in KvAP. S3 had low membrane insertion activity, whereas S4 possessed a unique type-I signal anchor (SA-I) function, which enabled it to insert into the membrane by itself. S4 was also found to function as a stop-transfer signal for retention in the membrane. The length and structural nature of the extracellular S3-S4 loop affected the membrane insertion of S3 and S4, suggesting that S3 membrane insertion was dependent on S4. Replacement of charged residues within the transmembrane regions with residues of opposite charge revealed that Asp72 in S2 and Glu93 in S3 contributed to membrane insertion of S3 and S4, and increased the stability of S4 in the membrane. These results indicate that the SA-I function of S4, unique among K+ channels studied to date, promotes the insertion of S3 into the membrane, and that the charged residues essential for voltage sensing contribute to the membrane-insertion of the voltage sensor domain in KvAP.
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202
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Stone TA, Schiller N, Workewych N, von Heijne G, Deber CM. Hydrophobic Clusters Raise the Threshold Hydrophilicity for Insertion of Transmembrane Sequences in Vivo. Biochemistry 2016; 55:5772-5779. [PMID: 27620701 DOI: 10.1021/acs.biochem.6b00650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Insertion of a nascent membrane protein segment by the translocon channel into the bilayer is naturally promoted by high segmental hydrophobicity, but its selection as a transmembrane (TM) segment is complicated by the diverse environments (aqueous vs lipidic) the protein encounters and by the fact that most TM segments contain a substantial amount (∼30%) of polar residues, as required for protein structural stabilization and/or function. To examine the contributions of these factors systematically, we designed and synthesized a peptide library consisting of pairs of compositionally identical, but sequentially different, peptides with 19-residue core sequences varying (i) in Leu positioning (with five or seven Leu residues clustered into a contiguous "block" in the middle of the segment or "scrambled" throughout the sequence) and (ii) in Ser content (0-6 residues). The library was analyzed by a combination of biophysical and biological techniques, including HPLC retention times, circular dichroism measurements of helicity in micelle and phospholipid bilayer media, and relative blue shifts in Trp fluorescence maxima, as well as by the extent of membrane insertion in a translocon-mediated assay using microsomal membranes from dog pancreas endoplasmic reticulum. We found that local blocks of high hydrophobicity heighten the translocon's propensity to insert moderately hydrophilic sequences, until a "threshold hydrophilicity" is surpassed whereby segments no longer insert even in the presence of Leu blocks. This study codifies the prerequisites of apolar/polar content and residue positioning that define nascent TM segments, illustrates the accuracy in their prediction, and highlights how a single disease-causing mutation can tip the balance toward anomalous translocation/insertion.
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Affiliation(s)
- Tracy A Stone
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children , Toronto M5G 0A4, Ontario, Canada.,Department of Biochemistry, University of Toronto , Toronto M5S 1A8, Ontario, Canada
| | - Nina Schiller
- Department of Biochemistry and Biophysics, Stockholm University , SE-106 91 Stockholm, Sweden.,Science for Life Laboratory, Stockholm University , Box 1031, SE-171 21 Solna, Sweden
| | - Natalie Workewych
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children , Toronto M5G 0A4, Ontario, Canada
| | - Gunnar von Heijne
- Department of Biochemistry and Biophysics, Stockholm University , SE-106 91 Stockholm, Sweden.,Science for Life Laboratory, Stockholm University , Box 1031, SE-171 21 Solna, Sweden
| | - Charles M Deber
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children , Toronto M5G 0A4, Ontario, Canada.,Department of Biochemistry, University of Toronto , Toronto M5S 1A8, Ontario, Canada
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203
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From Nanodiscs to Isotropic Bicelles: A Procedure for Solution Nuclear Magnetic Resonance Studies of Detergent-Sensitive Integral Membrane Proteins. Structure 2016; 24:1830-1841. [PMID: 27618661 DOI: 10.1016/j.str.2016.07.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 07/25/2016] [Accepted: 07/25/2016] [Indexed: 01/04/2023]
Abstract
Nanodiscs and isotropic bicelles are promising membrane mimetics in the field of solution nuclear magnetic resonance (NMR) spectroscopy of integral membrane proteins (IMPs). Despite varied challenges to solution NMR studies of IMPs, we attribute the paucity of solution NMR structures in these environments to the inability of diverse IMPs to withstand detergent treatment during standard nanodisc and bicelle preparations. Here, we present a strategy that creates small isotropic bicelles from IMPs co-translationally embedded in large nanodiscs using cell-free expression. Our results demonstrate appreciable gains in NMR spectral quality while preserving lipid-IMP contacts. We validate the approach on the detergent-sensitive LspA, which finally allowed us to perform high-quality triple-resonance NMR experiments for structural studies. Our strategy of producing bicelles from nanodiscs comprehensively avoids detergent during expression and preparation and is suitable for solution NMR spectroscopy of lipid-IMP complexes.
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204
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Energetics of side-chain snorkeling in transmembrane helices probed by nonproteinogenic amino acids. Proc Natl Acad Sci U S A 2016; 113:10559-64. [PMID: 27601675 DOI: 10.1073/pnas.1606776113] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cotranslational translocon-mediated insertion of membrane proteins into the endoplasmic reticulum is a key process in membrane protein biogenesis. Although the mechanism is understood in outline, quantitative data on the energetics of the process is scarce. Here, we have measured the effect on membrane integration efficiency of nonproteinogenic analogs of the positively charged amino acids arginine and lysine incorporated into model transmembrane segments. We provide estimates of the influence on the apparent free energy of membrane integration (ΔGapp) of "snorkeling" of charged amino acids toward the lipid-water interface, and of charge neutralization. We further determine the effect of fluorine atoms and backbone hydrogen bonds (H-bonds) on ΔGapp These results help establish a quantitative basis for our understanding of membrane protein assembly in eukaryotic cells.
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205
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Schuler EE, Nagarajan S, Dyer RB. Submillisecond Dynamics of Mastoparan X Insertion into Lipid Membranes. J Phys Chem Lett 2016; 7:3365-3370. [PMID: 27513014 PMCID: PMC5019822 DOI: 10.1021/acs.jpclett.6b01512] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The mechanism of protein insertion into a lipid bilayer is poorly understood because the kinetics of this process is difficult to measure. We developed a new approach to study insertion of the antimicrobial peptide Mastoparan X into zwitterionic lipid vesicles, using a laser-induced temperature-jump to initiate insertion on the microsecond time scale and infrared and fluorescence spectroscopies to follow the kinetics. Infrared probes the desolvation of the peptide backbone and yields biphasic kinetics with relaxation lifetimes of 12 and 117 μs, whereas fluorescence probes the intrinsic tryptophan residue located near the N-terminus and yields a single exponential phase with a lifetime of 440 μs. Arrhenius analysis of the temperature-dependent rates yields an activation energy for insertion of 96 kJ/mol. These results demonstrate the complexity of the insertion process and provide mechanistic insight into the interplay between peptides and the lipid bilayer required for peptide transport across cellular membranes.
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Affiliation(s)
| | | | - R. Brian Dyer
- Corresponding Author: Address: Emory University, Department of Chemistry, 1515 Dickey Drive, Atlanta, GA 30322. Phone: 404-727-6637;
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206
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Radchenko DS, Kattge S, Kara S, Ulrich AS, Afonin S. Does a methionine-to-norleucine substitution in PGLa influence peptide-membrane interactions? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2019-2027. [DOI: 10.1016/j.bbamem.2016.06.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 05/13/2016] [Accepted: 06/02/2016] [Indexed: 12/17/2022]
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207
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Kroncke BM, Duran AM, Mendenhall JL, Meiler J, Blume JD, Sanders CR. Documentation of an Imperative To Improve Methods for Predicting Membrane Protein Stability. Biochemistry 2016; 55:5002-9. [PMID: 27564391 PMCID: PMC5024705 DOI: 10.1021/acs.biochem.6b00537] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
There
is a compelling and growing need to accurately predict the
impact of amino acid mutations on protein stability for problems in
personalized medicine and other applications. Here the ability of
10 computational tools to accurately predict mutation-induced perturbation
of folding stability (ΔΔG) for membrane
proteins of known structure was assessed. All methods for predicting
ΔΔG values performed significantly worse
when applied to membrane proteins than when applied to soluble proteins,
yielding estimated concordance, Pearson, and Spearman correlation
coefficients of <0.4 for membrane proteins. Rosetta and PROVEAN
showed a modest ability to classify mutations as destabilizing (ΔΔG < −0.5 kcal/mol), with a 7 in 10 chance of correctly
discriminating a randomly chosen destabilizing variant from a randomly
chosen stabilizing variant. However, even this performance is significantly
worse than for soluble proteins. This study highlights the need for
further development of reliable and reproducible methods for predicting
thermodynamic folding stability in membrane proteins.
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Affiliation(s)
- Brett M Kroncke
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
| | - Amanda M Duran
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
| | - Jeffrey L Mendenhall
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
| | - Jens Meiler
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
| | - Jeffrey D Blume
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
| | - Charles R Sanders
- Department of Biochemistry, ‡Center for Structural Biology, §Departments of Chemistry, Pharmacology, and Bioinformatics, and ∥Department of Biostatistics, Vanderbilt University , Nashville, Tennessee 37240, United States
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208
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Gatsogiannis C, Merino F, Prumbaum D, Roderer D, Leidreiter F, Meusch D, Raunser S. Membrane insertion of a Tc toxin in near-atomic detail. Nat Struct Mol Biol 2016; 23:884-890. [PMID: 27571177 DOI: 10.1038/nsmb.3281] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 07/26/2016] [Indexed: 12/22/2022]
Abstract
Tc toxins from pathogenic bacteria use a special syringe-like mechanism to perforate the host cell membrane and inject a deadly enzyme into the host cytosol. The molecular mechanism of this unusual injection system is poorly understood. Using electron cryomicroscopy, we determined the structure of TcdA1 from Photorhabdus luminescens embedded in lipid nanodiscs. In our structure, compared with the previous structure of TcdA1 in the prepore state, the transmembrane helices rearrange in the membrane and open the initially closed pore. However, the helices do not span the complete membrane; instead, the loops connecting the helices form the rim of the funnel. Lipid head groups reach into the space between the loops and consequently stabilize the pore conformation. The linker domain is folded and packed into a pocket formed by the other domains of the toxin, thereby considerably contributing to stabilization of the pore state.
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Affiliation(s)
- Christos Gatsogiannis
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Daniel Prumbaum
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Daniel Roderer
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Franziska Leidreiter
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Dominic Meusch
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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209
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Zhang XC, Liu Z, Li J. From membrane tension to channel gating: A principal energy transfer mechanism for mechanosensitive channels. Protein Sci 2016; 25:1954-1964. [PMID: 27530280 DOI: 10.1002/pro.3017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 08/10/2016] [Indexed: 12/17/2022]
Abstract
Mechanosensitive (MS) channels are evolutionarily conserved membrane proteins that play essential roles in multiple cellular processes, including sensing mechanical forces and regulating osmotic pressure. Bacterial MscL and MscS are two prototypes of MS channels. Numerous structural studies, in combination with biochemical and cellular data, provide valuable insights into the mechanism of energy transfer from membrane tension to gating of the channel. We discuss these data in a unified two-state model of thermodynamics. In addition, we propose a lipid diffusion-mediated mechanism to explain the adaptation phenomenon of MscS.
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Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China.
| | - Zhenfeng Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China
| | - Jie Li
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China
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210
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Collinson I, Corey RA, Allen WJ. Channel crossing: how are proteins shipped across the bacterial plasma membrane? Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0025. [PMID: 26370937 PMCID: PMC4632601 DOI: 10.1098/rstb.2015.0025] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The structure of the first protein-conducting channel was determined more than a decade ago. Today, we are still puzzled by the outstanding problem of protein translocation—the dynamic mechanism underlying the consignment of proteins across and into membranes. This review is an attempt to summarize and understand the energy transducing capabilities of protein-translocating machines, with emphasis on bacterial systems: how polypeptides make headway against the lipid bilayer and how the process is coupled to the free energy associated with ATP hydrolysis and the transmembrane protein motive force. In order to explore how cargo is driven across the membrane, the known structures of the protein-translocation machines are set out against the background of the historic literature, and in the light of experiments conducted in their wake. The paper will focus on the bacterial general secretory (Sec) pathway (SecY-complex), and its eukaryotic counterpart (Sec61-complex), which ferry proteins across the membrane in an unfolded state, as well as the unrelated Tat system that assembles bespoke channels for the export of folded proteins.
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Affiliation(s)
- Ian Collinson
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Robin A Corey
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - William J Allen
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
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211
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Avci D, Lemberg MK. Clipping or Extracting: Two Ways to Membrane Protein Degradation. Trends Cell Biol 2016; 25:611-622. [PMID: 26410407 DOI: 10.1016/j.tcb.2015.07.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/18/2015] [Accepted: 07/17/2015] [Indexed: 12/20/2022]
Abstract
Protein degradation is a fundamentally important process that allows cells to recognize and remove damaged protein species and to regulate protein abundance according to functional need. A fundamental challenge is to understand how membrane proteins are recognized and removed from cellular organelles. While most of our understanding of this mechanism comes from studies on p97/Cdc48-mediated protein dislocation along the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway, recent studies have revealed intramembrane proteolysis to be an additional mechanism that can extract transmembrane segments. Here, we review these two principles in membrane protein degradation and discuss how intramembrane proteolysis, which introduces an irreversible step in protein dislocation, is used to drive regulated protein turnover.
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Affiliation(s)
- Dönem Avci
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Marius K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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212
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La Rosa C, Scalisi S, Lolicato F, Pannuzzo M, Raudino A. Lipid-assisted protein transport: A diffusion-reaction model supported by kinetic experiments and molecular dynamics simulations. J Chem Phys 2016; 144:184901. [DOI: 10.1063/1.4948323] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Carmelo La Rosa
- Department of Chemical Science, University of Catania, Viale A. Doria 6, I-95125 Catania, Italy
| | - Silvia Scalisi
- Department of Chemical Science, University of Catania, Viale A. Doria 6, I-95125 Catania, Italy
| | - Fabio Lolicato
- Department of Chemical Science, University of Catania, Viale A. Doria 6, I-95125 Catania, Italy
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Martina Pannuzzo
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Antonio Raudino
- Department of Chemical Science, University of Catania, Viale A. Doria 6, I-95125 Catania, Italy
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213
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Biological insertion of computationally designed short transmembrane segments. Sci Rep 2016; 6:23397. [PMID: 26987712 PMCID: PMC4796907 DOI: 10.1038/srep23397] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/07/2016] [Indexed: 12/28/2022] Open
Abstract
The great majority of helical membrane proteins are inserted co-translationally into the ER membrane through a continuous ribosome-translocon channel. The efficiency of membrane insertion depends on transmembrane (TM) helix amino acid composition, the helix length and the position of the amino acids within the helix. In this work, we conducted a computational analysis of the composition and location of amino acids in transmembrane helices found in membrane proteins of known structure to obtain an extensive set of designed polypeptide segments with naturally occurring amino acid distributions. Then, using an in vitro translation system in the presence of biological membranes, we experimentally validated our predictions by analyzing its membrane integration capacity. Coupled with known strategies to control membrane protein topology, these findings may pave the way to de novo membrane protein design.
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214
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Kida Y, Ishihara Y, Fujita H, Onishi Y, Sakaguchi M. Stability and flexibility of marginally hydrophobic-segment stalling at the endoplasmic reticulum translocon. Mol Biol Cell 2016; 27:930-40. [PMID: 26823014 PMCID: PMC4791137 DOI: 10.1091/mbc.e15-09-0672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/19/2016] [Indexed: 01/10/2023] Open
Abstract
Many membrane proteins are integrated into the endoplasmic reticulum membrane through the protein-conducting channel, the translocon. Transmembrane segments with insufficient hydrophobicity for membrane integration are frequently found in multispanning membrane proteins, and such marginally hydrophobic (mH) segments should be accommodated, at least transiently, at the membrane. Here we investigated how mH-segments stall at the membrane and their stability. Our findings show that mH-segments can be retained at the membrane without moving into the lipid phase and that such segments flank Sec61α, the core channel of the translocon, in the translational intermediate state. The mH-segments are gradually transferred from the Sec61 channel to the lipid environment in a hydrophobicity-dependent manner, and this lateral movement may be affected by the ribosome. In addition, stalling mH-segments allow for insertion of the following transmembrane segment, forming an Ncytosol/Clumen orientation, suggesting that mH-segments can move laterally to accommodate the next transmembrane segment. These findings suggest that mH-segments may be accommodated at the ER membrane with lateral fluctuation between the Sec61 channel and the lipid phase.
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Affiliation(s)
- Yuichiro Kida
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
| | - Yudai Ishihara
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
| | - Hidenobu Fujita
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
| | - Yukiko Onishi
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
| | - Masao Sakaguchi
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
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215
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Nilsson OB, Müller-Lucks A, Kramer G, Bukau B, von Heijne G. Trigger Factor Reduces the Force Exerted on the Nascent Chain by a Cotranslationally Folding Protein. J Mol Biol 2016; 428:1356-1364. [DOI: 10.1016/j.jmb.2016.02.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/02/2016] [Accepted: 02/03/2016] [Indexed: 10/22/2022]
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216
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Ried CL, Scharnagl C, Langosch D. Entrapment of Water at the Transmembrane Helix–Helix Interface of Quiescin Sulfhydryl Oxidase 2. Biochemistry 2016; 55:1287-90. [DOI: 10.1021/acs.biochem.5b01239] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christian L. Ried
- Lehrstuhl
Chemie der Biopolymere, Technische Universität München, Weihenstephaner
Berg 3, 85354 Freising, and Munich Center For Integrated Protein Science (CIPSM), Germany
| | - Christina Scharnagl
- Fakultät
für Physik E14, Technische Universität München, Maximus-von-Imhof-Forum
4, 85354 Freising, Germany
| | - Dieter Langosch
- Lehrstuhl
Chemie der Biopolymere, Technische Universität München, Weihenstephaner
Berg 3, 85354 Freising, and Munich Center For Integrated Protein Science (CIPSM), Germany
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217
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Gumbart JC, Chipot C. Decrypting protein insertion through the translocon with free-energy calculations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1663-71. [PMID: 26896694 DOI: 10.1016/j.bbamem.2016.02.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 02/11/2016] [Accepted: 02/12/2016] [Indexed: 12/23/2022]
Abstract
Protein insertion into a membrane is a complex process involving numerous players. The most prominent of these players is the Sec translocon complex, a conserved protein-conducting channel present in the cytoplasmic membrane of bacteria and the membrane of the endoplasmic reticulum in eukaryotes. The last decade has seen tremendous leaps forward in our understanding of how insertion is managed by the translocon and its partners, coming from atomic-detailed structures, innovative experiments, and well-designed simulations. In this review, we discuss how experiments and simulations, hand-in-hand, teased out the secrets of the translocon-facilitated membrane insertion process. In particular, we focus on the role of free-energy calculations in elucidating membrane insertion. Amazingly, despite all its apparent complexity, protein insertion into membranes is primarily driven by simple thermodynamic and kinetic principles. This article is part of a Special Issue entitled: Membrane proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| | - Christophe Chipot
- Laboratoire International Associé Centre National de la Recherche Scientifique and University of Illinois at Urbana-Champaign, UMR n° 7565, Université de Lorraine, B.P. 70239, 54506 Vandœuvre-lès-Nancy, France; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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218
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Elazar A, Weinstein J, Biran I, Fridman Y, Bibi E, Fleishman SJ. Mutational scanning reveals the determinants of protein insertion and association energetics in the plasma membrane. eLife 2016; 5:e12125. [PMID: 26824389 PMCID: PMC4786438 DOI: 10.7554/elife.12125] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 01/28/2016] [Indexed: 11/13/2022] Open
Abstract
Insertion of helix-forming segments into the membrane and their association determines the structure, function, and expression levels of all plasma membrane proteins. However, systematic and reliable quantification of membrane-protein energetics has been challenging. We developed a deep mutational scanning method to monitor the effects of hundreds of point mutations on helix insertion and self-association within the bacterial inner membrane. The assay quantifies insertion energetics for all natural amino acids at 27 positions across the membrane, revealing that the hydrophobicity of biological membranes is significantly higher than appreciated. We further quantitate the contributions to membrane-protein insertion from positively charged residues at the cytoplasm-membrane interface and reveal large and unanticipated differences among these residues. Finally, we derive comprehensive mutational landscapes in the membrane domains of Glycophorin A and the ErbB2 oncogene, and find that insertion and self-association are strongly coupled in receptor homodimers.
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Affiliation(s)
- Assaf Elazar
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Jonathan Weinstein
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Ido Biran
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Yearit Fridman
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Eitan Bibi
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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219
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Zhang H, Huang Q, Bei Z, Wei Y, Floudas CA. COMSAT: Residue contact prediction of transmembrane proteins based on support vector machines and mixed integer linear programming. Proteins 2016; 84:332-48. [PMID: 26756402 DOI: 10.1002/prot.24979] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 11/19/2015] [Accepted: 12/10/2015] [Indexed: 12/28/2022]
Abstract
In this article, we present COMSAT, a hybrid framework for residue contact prediction of transmembrane (TM) proteins, integrating a support vector machine (SVM) method and a mixed integer linear programming (MILP) method. COMSAT consists of two modules: COMSAT_SVM which is trained mainly on position-specific scoring matrix features, and COMSAT_MILP which is an ab initio method based on optimization models. Contacts predicted by the SVM model are ranked by SVM confidence scores, and a threshold is trained to improve the reliability of the predicted contacts. For TM proteins with no contacts above the threshold, COMSAT_MILP is used. The proposed hybrid contact prediction scheme was tested on two independent TM protein sets based on the contact definition of 14 Å between Cα-Cα atoms. First, using a rigorous leave-one-protein-out cross validation on the training set of 90 TM proteins, an accuracy of 66.8%, a coverage of 12.3%, a specificity of 99.3% and a Matthews' correlation coefficient (MCC) of 0.184 were obtained for residue pairs that are at least six amino acids apart. Second, when tested on a test set of 87 TM proteins, the proposed method showed a prediction accuracy of 64.5%, a coverage of 5.3%, a specificity of 99.4% and a MCC of 0.106. COMSAT shows satisfactory results when compared with 12 other state-of-the-art predictors, and is more robust in terms of prediction accuracy as the length and complexity of TM protein increase. COMSAT is freely accessible at http://hpcc.siat.ac.cn/COMSAT/.
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Affiliation(s)
- Huiling Zhang
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Qingsheng Huang
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhendong Bei
- Center for Cloud Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yanjie Wei
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Christodoulos A Floudas
- Department of Chemical Engineering, Texas A&M University, College Station, Texas, 77843.,Texas A&M Energy Institute, Texas A&M University, College Station, Texas, 77843
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220
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Romano FB, Tang Y, Rossi KC, Monopoli KR, Ross JL, Heuck AP. Type 3 Secretion Translocators Spontaneously Assemble a Hexadecameric Transmembrane Complex. J Biol Chem 2016; 291:6304-15. [PMID: 26786106 DOI: 10.1074/jbc.m115.681031] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Indexed: 11/06/2022] Open
Abstract
A type 3 secretion system is used by many bacterial pathogens to inject proteins into eukaryotic cells. Pathogens insert a translocon complex into the target eukaryotic membrane by secreting two proteins known as translocators. How these translocators form a translocon in the lipid bilayer and why both proteins are required remains elusive. Pseudomonas aeruginosa translocators PopB and PopD insert pores into membranes forming homo- or hetero-complexes of undetermined stoichiometry. Single-molecule fluorescence photobleaching experiments revealed that PopD formed mostly hexameric structures in membranes, whereas PopB displayed a bi-modal distribution with 6 and 12 subunits peaks. However, individually the proteins are not functional for effector translocation. We have found that when added together, the translocators formed distinct hetero-complexes containing 8 PopB and 8 PopD molecules. Thus, the interaction between PopB and PopD guide the assembly of a unique hetero-oligomer in membranes.
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Affiliation(s)
| | - Yuzhou Tang
- From the Program in Molecular and Cellular Biology, and
| | - Kyle C Rossi
- the Departments of Biochemistry and Molecular Biology and
| | | | - Jennifer L Ross
- From the Program in Molecular and Cellular Biology, and Physics, University of Massachusetts, Amherst, Massachusetts 01003
| | - Alejandro P Heuck
- From the Program in Molecular and Cellular Biology, and the Departments of Biochemistry and Molecular Biology and
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221
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A topological and conformational stability alphabet for multipass membrane proteins. Nat Chem Biol 2016; 12:167-73. [PMID: 26780406 DOI: 10.1038/nchembio.2001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 11/13/2015] [Indexed: 12/27/2022]
Abstract
Multipass membrane proteins perform critical signal transduction and transport across membranes. How transmembrane helix (TMH) sequences encode the topology and conformational flexibility regulating these functions remains poorly understood. Here we describe a comprehensive analysis of the sequence-structure relationships at multiple interacting TMHs from all membrane proteins with structures in the Protein Data Bank (PDB). We found that membrane proteins can be deconstructed in interacting TMH trimer units, which mostly fold into six distinct structural classes of topologies and conformations. Each class is enriched in recurrent sequence motifs from functionally unrelated proteins, revealing unforeseen consensus and evolutionary conserved networks of stabilizing interhelical contacts. Interacting TMHs' topology and local protein conformational flexibility were remarkably well predicted in a blinded fashion from the identified binding-hotspot motifs. Our results reveal universal sequence-structure principles governing the complex anatomy and plasticity of multipass membrane proteins that may guide de novo structure prediction, design, and studies of folding and dynamics.
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222
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Yue T, Sun M, Zhang S, Ren H, Ge B, Huang F. How transmembrane peptides insert and orientate in biomembranes: a combined experimental and simulation study. Phys Chem Chem Phys 2016; 18:17483-94. [DOI: 10.1039/c6cp01133k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
After the synthesis of transmembrane peptides/proteins (TMPs), their insertion into a lipid bilayer is a fundamental biophysical process.
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Affiliation(s)
- Tongtao Yue
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
| | - Mingbin Sun
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
| | - Shuai Zhang
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
| | - Hao Ren
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
| | - Baosheng Ge
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering and Biotechnology
- China University of Petroleum (East China)
- Qingdao
- China
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223
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Borrell JH, Domènech Ò, Keough KMW. Molecular Membrane Biochemistry. MEMBRANE PROTEIN – LIPID INTERACTIONS: PHYSICS AND CHEMISTRY IN THE BILAYER 2016. [DOI: 10.1007/978-3-319-30277-5_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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224
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Yang Z, Brouillette CG. A Guide to Differential Scanning Calorimetry of Membrane and Soluble Proteins in Detergents. Methods Enzymol 2016; 567:319-58. [DOI: 10.1016/bs.mie.2015.08.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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225
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Maity A, Sinha S, Ganguly D, Ghosh Dastidar S. C-terminal tail insertion of Bcl-xL in membrane occurs via partial unfolding and refolding cycle associating microsolvation. Phys Chem Chem Phys 2016; 18:24095-105. [DOI: 10.1039/c6cp02468h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Insertion of the Bcl-xL C-terminal into the mitochondrial outer membrane is found to be guided by the partial unfolding–refolding cycle, assisted by micro-solvation.
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Affiliation(s)
- Atanu Maity
- Bioinformatics Centre
- Bose Institute
- P-1/12 CIT Scheme VII M
- Kolkata 700054
- India
| | - Souvik Sinha
- Bioinformatics Centre
- Bose Institute
- P-1/12 CIT Scheme VII M
- Kolkata 700054
- India
| | - Debabani Ganguly
- Department of Chemistry
- Indian Institute of Engineering Science and Technology
- Howrah-711103
- India
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226
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Abstract
Which properties of the membrane environment are essential for the folding and oligomerization of transmembrane proteins? Because the lipids that surround membrane proteins in situ spontaneously organize into bilayers, it may seem intuitive that interactions with the bilayer provide both hydrophobic and topological constraints that help the protein to achieve a stable and functional three-dimensional structure. However, one may wonder whether folding is actually driven by the membrane environment or whether the folded state just reflects an adaptation of integral proteins to the medium in which they function. Also, apart from the overall transmembrane orientation, might the asymmetry inherent in biosynthesis processes cause proteins to fold to out-of-equilibrium, metastable topologies? Which of the features of a bilayer are essential for membrane protein folding, and which are not? To which extent do translocons dictate transmembrane topologies? Recent data show that many membrane proteins fold and oligomerize very efficiently in media that bear little similarity to a membrane, casting doubt on the essentiality of many bilayer constraints. In the following discussion, we argue that some of the features of bilayers may contribute to protein folding, stability and regulation, but they are not required for the basic three-dimensional structure to be achieved. This idea, if correct, would imply that evolution has steered membrane proteins toward an accommodation to biosynthetic pathways and a good fit into their environment, but that their folding is not driven by the latter or dictated by insertion apparatuses. In other words, the three-dimensional structure of membrane proteins is essentially determined by intramolecular interactions and not by bilayer constraints and insertion pathways. Implications are discussed.
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Affiliation(s)
- Jean-Luc Popot
- Centre National de la Recherche Scientifique/Université Paris-7 UMR 7099 , Institut de Biologie Physico-Chimique (FRC 550), 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France
| | - Donald M Engelman
- Department of Molecular Biophysics and Biochemistry, Yale University , Box 208114, New Haven, Connecticut 06520-8114, United States
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227
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Affiliation(s)
- Stefan Pfeffer
- a Department of Molecular Structural Biology , Max-Planck Institute of Biochemistry , Martinsried , Germany
| | - Friedrich Förster
- a Department of Molecular Structural Biology , Max-Planck Institute of Biochemistry , Martinsried , Germany
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228
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Niwa T, Sasaki Y, Uemura E, Nakamura S, Akiyama M, Ando M, Sawada S, Mukai SA, Ueda T, Taguchi H, Akiyoshi K. Comprehensive study of liposome-assisted synthesis of membrane proteins using a reconstituted cell-free translation system. Sci Rep 2015; 5:18025. [PMID: 26667602 PMCID: PMC4678891 DOI: 10.1038/srep18025] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/03/2015] [Indexed: 02/02/2023] Open
Abstract
Membrane proteins play pivotal roles in cellular processes and are key targets for drug discovery. However, the reliable synthesis and folding of membrane proteins are significant problems that need to be addressed owing to their extremely high hydrophobic properties, which promote irreversible aggregation in hydrophilic conditions. Previous reports have suggested that protein aggregation could be prevented by including exogenous liposomes in cell-free translation processes. Systematic studies that identify which membrane proteins can be rescued from irreversible aggregation during translation by liposomes would be valuable in terms of understanding the effects of liposomes and developing applications for membrane protein engineering in the context of pharmaceutical science and nanodevice development. Therefore, we performed a comprehensive study to evaluate the effects of liposomes on 85 aggregation-prone membrane proteins from Escherichia coli by using a reconstituted, chemically defined cell-free translation system. Statistical analyses revealed that the presence of liposomes increased the solubility of >90% of the studied membrane proteins, and ultimately improved the yields of the synthesized proteins. Bioinformatics analyses revealed significant correlations between the liposome effect and the physicochemical properties of the membrane proteins.
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Affiliation(s)
- Tatsuya Niwa
- Department of Biomolecular Engineering, Graduate School of Biosciences and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
| | - Yoshihiro Sasaki
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Eri Uemura
- Department of Biomolecular Engineering, Graduate School of Biosciences and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
| | - Shugo Nakamura
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan
| | - Minato Akiyama
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Mitsuru Ando
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Japan Science and Technology Agency (JST), The Exploratory Research for Advanced Technology (ERATO), Bio-nanotransporter Project, Katsura Int'tech Center, Katsura, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Shinichi Sawada
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Japan Science and Technology Agency (JST), The Exploratory Research for Advanced Technology (ERATO), Bio-nanotransporter Project, Katsura Int'tech Center, Katsura, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Sada-atu Mukai
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Japan Science and Technology Agency (JST), The Exploratory Research for Advanced Technology (ERATO), Bio-nanotransporter Project, Katsura Int'tech Center, Katsura, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Takuya Ueda
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, FSB401, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan
| | - Hideki Taguchi
- Department of Biomolecular Engineering, Graduate School of Biosciences and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
| | - Kazunari Akiyoshi
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Japan Science and Technology Agency (JST), The Exploratory Research for Advanced Technology (ERATO), Bio-nanotransporter Project, Katsura Int'tech Center, Katsura, Nishikyo-ku, Kyoto 615-8530, Japan
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229
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Vorobyov I, Kim I, Chu ZT, Warshel A. Refining the treatment of membrane proteins by coarse-grained models. Proteins 2015; 84:92-117. [PMID: 26531155 DOI: 10.1002/prot.24958] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/19/2015] [Accepted: 10/23/2015] [Indexed: 01/19/2023]
Abstract
Obtaining a quantitative description of the membrane proteins stability is crucial for understanding many biological processes. However the advance in this direction has remained a major challenge for both experimental studies and molecular modeling. One of the possible directions is the use of coarse-grained models but such models must be carefully calibrated and validated. Here we use a recent progress in benchmark studies on the energetics of amino acid residue and peptide membrane insertion and membrane protein stability in refining our previously developed coarse-grained model (Vicatos et al., Proteins 2014;82:1168). Our refined model parameters were fitted and/or tested to reproduce water/membrane partitioning energetics of amino acid side chains and a couple of model peptides. This new model provides a reasonable agreement with experiment for absolute folding free energies of several β-barrel membrane proteins as well as effects of point mutations on a relative stability for one of those proteins, OmpLA. The consideration and ranking of different rotameric states for a mutated residue was found to be essential to achieve satisfactory agreement with the reference data.
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Affiliation(s)
- Igor Vorobyov
- Department of Chemistry, University of Southern California, Los Angeles, California, 90089-1062
| | - Ilsoo Kim
- Department of Chemistry, University of Southern California, Los Angeles, California, 90089-1062
| | - Zhen T Chu
- Department of Chemistry, University of Southern California, Los Angeles, California, 90089-1062
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, Los Angeles, California, 90089-1062
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230
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Chi H, Wang X, Li J, Ren H, Huang F. Folding of newly translated membrane protein CCR5 is assisted by the chaperonin GroEL-GroES. Sci Rep 2015; 5:17037. [PMID: 26585937 PMCID: PMC4653635 DOI: 10.1038/srep17037] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/23/2015] [Indexed: 01/20/2023] Open
Abstract
The in vitro folding of newly translated human CC chemokine receptor type 5
(CCR5), which belongs to the physiologically important family of G protein-coupled
receptors (GPCRs), has been studied in a cell-free system supplemented with the
surfactant Brij-35. The freshly synthesized CCR5 can spontaneously fold into its
biologically active state but only slowly and inefficiently. However, on addition of
the GroEL-GroES molecular chaperone system, the folding of the nascent CCR5 was
significantly enhanced, as was the structural stability and functional expression of
the soluble form of CCR5. The chaperonin GroEL was partially effective on its own,
but for maximum efficiency both the GroEL and its GroES lid were necessary. These
results are direct evidence for chaperone-assisted membrane protein folding and
therefore demonstrate that GroEL-GroES may be implicated in the folding of membrane
proteins.
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Affiliation(s)
- Haixia Chi
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, P. R. China
| | - Xiaoqiang Wang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, P. R. China
| | - Jiqiang Li
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, P. R. China
| | - Hao Ren
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, P. R. China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, P. R. China
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231
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Abstract
A new simulation protocol has revealed unexpected complexity in the folding of membrane proteins.
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Affiliation(s)
- Stephen H White
- Department of Physiology & Biophysics, University of California, Irvine, Irvine, United States
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232
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Min D, Jefferson RE, Bowie JU, Yoon TY. Mapping the energy landscape for second-stage folding of a single membrane protein. Nat Chem Biol 2015; 11:981-7. [PMID: 26479439 DOI: 10.1038/nchembio.1939] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/14/2015] [Indexed: 12/15/2022]
Abstract
Membrane proteins are designed to fold and function in a lipid membrane, yet folding experiments within a native membrane environment are challenging to design. Here we show that single-molecule forced unfolding experiments can be adapted to study helical membrane protein folding under native-like bicelle conditions. Applying force using magnetic tweezers, we find that a transmembrane helix protein, Escherichia coli rhomboid protease GlpG, unfolds in a highly cooperative manner, largely unraveling as one physical unit in response to mechanical tension above 25 pN. Considerable hysteresis is observed, with refolding occurring only at forces below 5 pN. Characterizing the energy landscape reveals only modest thermodynamic stability (ΔG = 6.5 kBT) but a large unfolding barrier (21.3 kBT) that can maintain the protein in a folded state for long periods of time (t1/2 ∼3.5 h). The observed energy landscape may have evolved to limit the existence of troublesome partially unfolded states and impart rigidity to the structure.
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Affiliation(s)
- Duyoung Min
- National Creative Research Initiative Center for Single-Molecule Systems Biology, KAIST, Daejeon, South Korea.,Department of Physics, KAIST, Daejeon, South Korea
| | - Robert E Jefferson
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, USA
| | - James U Bowie
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, USA
| | - Tae-Young Yoon
- National Creative Research Initiative Center for Single-Molecule Systems Biology, KAIST, Daejeon, South Korea.,Department of Physics, KAIST, Daejeon, South Korea
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233
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Madhusudan Makwana K, Mahalakshmi R. Implications of aromatic-aromatic interactions: From protein structures to peptide models. Protein Sci 2015; 24:1920-33. [PMID: 26402741 DOI: 10.1002/pro.2814] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 09/17/2015] [Accepted: 09/18/2015] [Indexed: 12/11/2022]
Abstract
With increasing structural information on proteins, the opportunity to understand physical forces governing protein folding is also expanding. One of the significant non-covalent forces between the protein side chains is aromatic-aromatic interactions. Aromatic interactions have been widely exploited and thoroughly investigated in the context of folding, stability, molecular recognition, and self-assembly processes. Through this review, we discuss the contribution of aromatic interactions to the activity and stability of thermophilic, mesophilic, and psychrophilic proteins. Being hydrophobic, aromatic amino acids tend to reside in the protein hydrophobic interior or transmembrane segments of proteins. In such positions, it can play a diverse role in soluble and membrane proteins, and in α-helix and β-sheet stabilization. We also highlight here some excellent investigations made using peptide models and several approaches involving aryl-aryl interactions, as an increasingly popular strategy in protein and peptide engineering. A recent survey described the existence of aromatic clusters (trimer, tetramer, pentamer, and higher order assemblies), revealing the self-associating property of aryl groups, even in folded protein structures. The application of this self-assembly of aromatics in the generation of modern bionanomaterials is also discussed.
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Affiliation(s)
- Kamlesh Madhusudan Makwana
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, 462023, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, 462023, India
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234
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Abstract
SIGNIFICANCE Selenoproteins employ selenium to supplement the chemistry available through the common 20 amino acids. These powerful enzymes are affiliated with redox biology, often in connection with the detection, management, and signaling of oxidative stress. Among them, membrane-bound selenoproteins play prominent roles in signaling pathways, Ca(2+) regulation, membrane complexes integrity, and biosynthesis of lipophilic molecules. RECENT ADVANCES The number of selenoproteins whose physiological roles, protein partners, expression, evolution, and biosynthesis are characterized is steadily increasing, thus offering a more nuanced view of this specialized family. This review focuses on human membrane selenoproteins, particularly the five least characterized ones: selenoproteins I, K, N, S, and T. CRITICAL ISSUES Membrane-bound selenoproteins are the least understood, as it is challenging to provide the membrane-like environment required for their biochemical and biophysical characterization. Hence, their studies rely mostly on biological rather than structural and biochemical assays. Another aspect that has not received much attention is the particular role that their membrane association plays in their physiological function. FUTURE DIRECTIONS Findings cited in this review show that it is possible to infer the structure and the membrane-binding mode of these lesser-studied selenoproteins and design experiments to examine the role of the rare amino acid selenocysteine.
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Affiliation(s)
- Jun Liu
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware
| | - Sharon Rozovsky
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware
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235
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Structure of the native Sec61 protein-conducting channel. Nat Commun 2015; 6:8403. [PMID: 26411746 PMCID: PMC4598622 DOI: 10.1038/ncomms9403] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/19/2015] [Indexed: 12/12/2022] Open
Abstract
In mammalian cells, secretory and membrane proteins are translocated across or inserted into the endoplasmic reticulum (ER) membrane by the universally conserved protein-conducting channel Sec61, which has been structurally studied in isolated, detergent-solubilized states. Here we structurally and functionally characterize native, non-solubilized ribosome-Sec61 complexes on rough ER vesicles using cryo-electron tomography and ribosome profiling. Surprisingly, the 9-Å resolution subtomogram average reveals Sec61 in a laterally open conformation, even though the channel is not in the process of inserting membrane proteins into the lipid bilayer. In contrast to recent mechanistic models for polypeptide translocation and insertion, our results indicate that the laterally open conformation of Sec61 is the only conformation present in the ribosome-bound translocon complex, independent of its functional state. Consistent with earlier functional studies, our structure suggests that the ribosome alone, even without a nascent chain, is sufficient for lateral opening of Sec61 in a lipid environment. The protein-conducting channel Sec61 is responsible for protein transport and membrane insertion at the endoplasmic reticulum. Here, the authors determine the structure of ribosome-bound Sec61 in a native context, in which it adopts a laterally open conformation, irrespective of its functional state.
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236
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Van Lehn RC, Zhang B, Miller TF. Regulation of multispanning membrane protein topology via post-translational annealing. eLife 2015; 4. [PMID: 26408961 PMCID: PMC4635508 DOI: 10.7554/elife.08697] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/25/2015] [Indexed: 12/19/2022] Open
Abstract
The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis. DOI:http://dx.doi.org/10.7554/eLife.08697.001 Proteins are long chains of smaller molecules called amino acids, and are built inside cells by a molecular machine called the ribosome. Many important proteins must be inserted into the membrane that surrounds each cell in order to carry out their role. As these proteins are being built by the ribosome, they thread their way into a membrane-spanning channel (called the translocon) from the inner side of the membrane. Short segments of these integral membrane proteins (called transmembrane domains) then become embedded in the membrane, while other parts of the protein remain on either side of the membrane. For a membrane protein to work properly, the end of each of its transmembrane domains must be on the correct side of the membrane (i.e., the protein must obtain the correct ‘topology’). The conventional model for this process suggests that topology is fixed when the first transmembrane domain of a protein is initially integrated into the membrane, while the ribosome is still building the protein. This model can explain most integral membrane proteins, which only have a single topology. However, it cannot explain the family of membrane proteins that have an almost equal chance of adopting one of two different topologies (so-called ‘dual-topology proteins’). Van Lehn et al. have now used computer modeling to simulate how a bacterial protein called EmrE (which is a dual-topology protein) integrates into the membrane via the translocon. The results reveal that a few transmembrane domains in EmrE do not fully integrate into the membrane while the ribosome is building the protein. Instead, these transmembrane domains slowly integrate after the ribosome has finished its job. These findings contradict the conventional model and suggest that some membrane proteins only become fully integrated after the protein-building process is complete. The next step in this work is to experimentally test predictions from the computer simulations. DOI:http://dx.doi.org/10.7554/eLife.08697.002
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Affiliation(s)
- Reid C Van Lehn
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Bin Zhang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Thomas F Miller
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
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237
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Magenau AJD, Richards JA, Pasquinelli MA, Savin DA, Mathers RT. Systematic Insights from Medicinal Chemistry To Discern the Nature of Polymer Hydrophobicity. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b01758] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Andrew J. D. Magenau
- Materials
Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Jeffrey A. Richards
- Department
of Chemistry, Pennsylvania State University, New Kensington, Pennsylvania 15068, United States
| | - Melissa A. Pasquinelli
- Fiber
and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Daniel A. Savin
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Robert T. Mathers
- Department
of Chemistry, Pennsylvania State University, New Kensington, Pennsylvania 15068, United States
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238
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Zhang XC, Zhao Y, Heng J, Jiang D. Energy coupling mechanisms of MFS transporters. Protein Sci 2015; 24:1560-79. [PMID: 26234418 DOI: 10.1002/pro.2759] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/27/2015] [Accepted: 07/28/2015] [Indexed: 01/01/2023]
Abstract
Major facilitator superfamily (MFS) is a large class of secondary active transporters widely expressed across all life kingdoms. Although a common 12-transmembrane helix-bundle architecture is found in most MFS crystal structures available, a common mechanism of energy coupling remains to be elucidated. Here, we discuss several models for energy-coupling in the transport process of the transporters, largely based on currently available structures and the results of their biochemical analyses. Special attention is paid to the interaction between protonation and the negative-inside membrane potential. Also, functional roles of the conserved sequence motifs are discussed in the context of the 3D structures. We anticipate that in the near future, a unified picture of the functions of MFS transporters will emerge from the insights gained from studies of the common architectures and conserved motifs.
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Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 100101
| | - Yan Zhao
- National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 100101
| | - Jie Heng
- National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 100101
| | - Daohua Jiang
- National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, 100101
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239
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Impact of holdase chaperones Skp and SurA on the folding of β-barrel outer-membrane proteins. Nat Struct Mol Biol 2015; 22:795-802. [PMID: 26344570 DOI: 10.1038/nsmb.3087] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 08/13/2015] [Indexed: 12/27/2022]
Abstract
Chaperones increase the folding yields of soluble proteins by suppressing misfolding and aggregation, but how they modulate the folding of integral membrane proteins is not well understood. Here we use single-molecule force spectroscopy and NMR spectroscopy to observe the periplasmic holdase chaperones SurA and Skp shaping the folding trajectory of the large β-barrel outer-membrane receptor FhuA from Escherichia coli. Either chaperone prevents FhuA from misfolding by stabilizing a dynamic, unfolded state, thus allowing the substrate to search for structural intermediates. During this search, the SurA-chaperoned FhuA polypeptide inserts β-hairpins into the membrane in a stepwise manner until the β-barrel is folded. The membrane acts as a free-energy sink for β-hairpin insertion and physically separates transient folds from chaperones. This stabilization of dynamic unfolded states and the trapping of folding intermediates funnel the FhuA polypeptide toward the native conformation.
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240
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Bohnert M, Pfanner N, van der Laan M. Mitochondrial machineries for insertion of membrane proteins. Curr Opin Struct Biol 2015; 33:92-102. [DOI: 10.1016/j.sbi.2015.07.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/13/2015] [Accepted: 07/27/2015] [Indexed: 01/08/2023]
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241
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Abstract
The heterotrimeric SecY translocon complex is required for the cotranslational assembly of membrane proteins in bacteria and archaea. The insertion of transmembrane (TM) segments during nascent-chain passage through the translocon is generally viewed as a simple partitioning process between the water-filled translocon and membrane lipid bilayer, suggesting that partitioning is driven by the hydrophobic effect. Indeed, the apparent free energy of partitioning of unnatural aliphatic amino acids on TM segments is proportional to accessible surface area, which is a hallmark of the hydrophobic effect [Öjemalm K, et al. (2011) Proc Natl Acad Sci USA 108(31):E359-E364]. However, the apparent partitioning solvation parameter is less than one-half the value expected for simple bulk partitioning, suggesting that the water in the translocon departs from bulk behavior. To examine the state of water in a SecY translocon complex embedded in a lipid bilayer, we carried out all-atom molecular-dynamics simulations of the Pyrococcus furiosus SecYE, which was determined to be in a "primed" open state [Egea PF, Stroud RM (2010) Proc Natl Acad Sci USA 107(40):17182-17187]. Remarkably, SecYE remained in this state throughout our 450-ns simulation. Water molecules within SecY exhibited anomalous diffusion, had highly retarded rotational dynamics, and aligned their dipoles along the SecY transmembrane axis. The translocon is therefore not a simple water-filled pore, which raises the question of how anomalous water behavior affects the mechanism of translocon function and, more generally, the partitioning of hydrophobic molecules. Because large water-filled cavities are found in many membrane proteins, our findings may have broader implications.
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242
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Stansfeld PJ, Goose JE, Caffrey M, Carpenter EP, Parker JL, Newstead S, Sansom MSP. MemProtMD: Automated Insertion of Membrane Protein Structures into Explicit Lipid Membranes. Structure 2015; 23:1350-61. [PMID: 26073602 PMCID: PMC4509712 DOI: 10.1016/j.str.2015.05.006] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 04/24/2015] [Accepted: 05/02/2015] [Indexed: 01/26/2023]
Abstract
There has been exponential growth in the number of membrane protein structures determined. Nevertheless, these structures are usually resolved in the absence of their lipid environment. Coarse-grained molecular dynamics (CGMD) simulations enable insertion of membrane proteins into explicit models of lipid bilayers. We have automated the CGMD methodology, enabling membrane protein structures to be identified upon their release into the PDB and embedded into a membrane. The simulations are analyzed for protein-lipid interactions, identifying lipid binding sites, and revealing local bilayer deformations plus molecular access pathways within the membrane. The coarse-grained models of membrane protein/bilayer complexes are transformed to atomistic resolution for further analysis and simulation. Using this automated simulation pipeline, we have analyzed a number of recently determined membrane protein structures to predict their locations within a membrane, their lipid/protein interactions, and the functional implications of an enhanced understanding of the local membrane environment of each protein. A simulation pipeline for predicting the location of a membrane protein in a bilayer A protocol for identifying novel membrane protein structures in the PDB Analysis of lipid binding sites and local bilayer deformation by membrane proteins Functional implications from enhanced understanding of local membrane environments
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Affiliation(s)
- Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Joseph E Goose
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Martin Caffrey
- Schools of Medicine and Biochemistry & Immunology, Trinity College Dublin, 152-160 Pearse Street, Dublin 2, Ireland
| | - Elisabeth P Carpenter
- Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Joanne L Parker
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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243
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De Marothy MT, Elofsson A. Marginally hydrophobic transmembrane α-helices shaping membrane protein folding. Protein Sci 2015; 24:1057-74. [PMID: 25970811 DOI: 10.1002/pro.2698] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 04/24/2015] [Indexed: 01/12/2023]
Abstract
Cells have developed an incredible machinery to facilitate the insertion of membrane proteins into the membrane. While we have a fairly good understanding of the mechanism and determinants of membrane integration, more data is needed to understand the insertion of membrane proteins with more complex insertion and folding pathways. This review will focus on marginally hydrophobic transmembrane helices and their influence on membrane protein folding. These weakly hydrophobic transmembrane segments are by themselves not recognized by the translocon and therefore rely on local sequence context for membrane integration. How can such segments reside within the membrane? We will discuss this in the light of features found in the protein itself as well as the environment it resides in. Several characteristics in proteins have been described to influence the insertion of marginally hydrophobic helices. Additionally, the influence of biological membranes is significant. To begin with, the actual cost for having polar groups within the membrane may not be as high as expected; the presence of proteins in the membrane as well as characteristics of some amino acids may enable a transmembrane helix to harbor a charged residue. The lipid environment has also been shown to directly influence the topology as well as membrane boundaries of transmembrane helices-implying a dynamic relationship between membrane proteins and their environment.
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Affiliation(s)
- Minttu T De Marothy
- Department of Biochemistry and Biophysics Science for Life Laboratory, Stockholm University, Solna, SE-171 21, Sweden
| | - Arne Elofsson
- Department of Biochemistry and Biophysics Science for Life Laboratory, Stockholm University, Solna, SE-171 21, Sweden
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244
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Peptide Folding in Translocon-Like Pores. J Membr Biol 2015; 248:407-17. [DOI: 10.1007/s00232-015-9808-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/05/2015] [Indexed: 10/23/2022]
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245
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Finkenwirth F, Sippach M, Landmesser H, Kirsch F, Ogienko A, Grunzel M, Kiesler C, Steinhoff HJ, Schneider E, Eitinger T. ATP-dependent Conformational Changes Trigger Substrate Capture and Release by an ECF-type Biotin Transporter. J Biol Chem 2015; 290:16929-42. [PMID: 25991724 DOI: 10.1074/jbc.m115.654343] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Indexed: 11/06/2022] Open
Abstract
Energy-coupling factor (ECF) transporters for vitamins and metal ions in prokaryotes consist of two ATP-binding cassette-type ATPases, a substrate-specific transmembrane protein (S component) and a transmembrane protein (T component) that physically interacts with the ATPases and the S component. The mechanism of ECF transporters was analyzed upon reconstitution of a bacterial biotin transporter into phospholipid bilayer nanodiscs. ATPase activity was not stimulated by biotin and was only moderately reduced by vanadate. A non-hydrolyzable ATP analog was a competitive inhibitor. As evidenced by cross-linking of monocysteine variants and by site-specific spin labeling of the Q-helix followed by EPR-based interspin distance analyses, closure and reopening of the ATPase dimer (BioM2) was a consequence of ATP binding and hydrolysis, respectively. A previously suggested role of a stretch of small hydrophobic amino acid residues within the first transmembrane segment of the S units for S unit/T unit interactions was structurally and functionally confirmed for the biotin transporter. Cross-linking of this segment in BioY (S) using homobifunctional thiol-reactive reagents to a coupling helix of BioN (T) indicated a reorientation rather than a disruption of the BioY/BioN interface during catalysis. Fluorescence emission of BioY labeled with an environmentally sensitive fluorophore was compatible with an ATP-induced reorientation and consistent with a hypothesized toppling mechanism. As demonstrated by [(3)H]biotin capture assays, ATP binding stimulated substrate capture by the transporter, and subsequent ATP hydrolysis led to substrate release. Our study represents the first experimental insight into the individual steps during the catalytic cycle of an ECF transporter in a lipid environment.
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Affiliation(s)
| | - Michael Sippach
- the Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany
| | - Heidi Landmesser
- Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany and
| | | | | | | | | | - Heinz-Jürgen Steinhoff
- the Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany
| | - Erwin Schneider
- Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany and
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246
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Editorial Overview: Elucidation of Protein Translocation Pathways, Part I. J Mol Biol 2015; 427:997-8. [DOI: 10.1016/j.jmb.2015.01.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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247
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Satoh T, Ohba A, Liu Z, Inagaki T, Satoh AK. dPob/EMC is essential for biosynthesis of rhodopsin and other multi-pass membrane proteins in Drosophila photoreceptors. eLife 2015; 4. [PMID: 25715730 PMCID: PMC4341237 DOI: 10.7554/elife.06306] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 01/26/2015] [Indexed: 12/22/2022] Open
Abstract
In eukaryotes, most integral membrane proteins are synthesized, integrated into the membrane, and folded properly in the endoplasmic reticulum (ER). We screened the mutants affecting rhabdomeric expression of rhodopsin 1 (Rh1) in the Drosophila photoreceptors and found that dPob/EMC3, EMC1, and EMC8/9, Drosophila homologs of subunits of ER membrane protein complex (EMC), are essential for stabilization of immature Rh1 in an earlier step than that at which another Rh1-specific chaperone (NinaA) acts. dPob/EMC3 localizes to the ER and associates with EMC1 and calnexin. Moreover, EMC is required for the stable expression of other multi-pass transmembrane proteins such as minor rhodopsins Rh3 and Rh4, transient receptor potential, and Na+K+-ATPase, but not for a secreted protein or type I single-pass transmembrane proteins. Furthermore, we found that dPob/EMC3 deficiency induces rhabdomere degeneration in a light-independent manner. These results collectively indicate that EMC is a key factor in the biogenesis of multi-pass transmembrane proteins, including Rh1, and its loss causes retinal degeneration. DOI:http://dx.doi.org/10.7554/eLife.06306.001 The membranes that surround cells contain many proteins, and those that span the entire width of the membrane are known as transmembrane proteins. Rhodopsin is one such transmembrane protein that is found in the light-sensitive ‘photoreceptor’ cells of the eye, where it plays an essential role in vision. Transmembrane proteins are made inside the cell and are inserted into the membrane surrounding a compartment called the endoplasmic reticulum. Here, they mature and ‘fold’ into their correct three-dimensional shape with help from chaperone proteins. Once correctly folded, the transmembrane proteins can be transported to the cell membrane. Incorrect folding of proteins can have severe consequences; if rhodopsin is incorrectly folded the photoreceptor cells can die, leading to blindness in humans and other animals. Experiments carried out in zebrafish have shown that the chaperone protein Pob is required for the survival of photoreceptor cells. Pob is part of a group or ‘complex’ of chaperone proteins in the endoplasmic reticulum called the EMC complex. This suggests that the EMC complex may be involved in folding rhodopsin, but the details remain unclear. Here, Satoh et al. studied the role of the EMC complex in the folding of rhodopsin in fruit flies. This involved examining hundreds of flies that carried a variety of genetic mutations and that also had low levels of rhodopsin. The experiments show that dPob—the fly version of Pob—and two other proteins in the EMC complex are required for newly-made rhodopsin to be stabilized. If photoreceptor cells are missing proteins from the complex, the light-sensitive structures in the eye degenerate. Rhodopsin is known as a ‘multi-pass’ membrane protein because it crosses the membrane multiple times. Satoh et al. found that the EMC complex is also required for the folding of other multi-pass membrane proteins in photoreceptor cells. The next challenge will be to reveal how the EMC complex is able to specifically target this type of transmembrane protein. DOI:http://dx.doi.org/10.7554/eLife.06306.002
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Affiliation(s)
- Takunori Satoh
- Graduate School of Integrated Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan
| | - Aya Ohba
- Graduate School of Integrated Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan
| | - Ziguang Liu
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, China
| | - Tsuyoshi Inagaki
- Graduate School of Integrated Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan
| | - Akiko K Satoh
- Graduate School of Integrated Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan
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248
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Stone TA, Schiller N, von Heijne G, Deber CM. Hydrophobic blocks facilitate lipid compatibility and translocon recognition of transmembrane protein sequences. Biochemistry 2015; 54:1465-73. [PMID: 25635746 PMCID: PMC4341838 DOI: 10.1021/bi5014886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
![]()
Biophysical hydrophobicity scales
suggest that partitioning of
a protein segment from an aqueous phase into a membrane is governed
by its perceived segmental hydrophobicity but do not establish specifically
(i) how the segment is identified in vivo for translocon-mediated
insertion or (ii) whether the destination lipid bilayer is biochemically
receptive to the inserted sequence. To examine the congruence between
these dual requirements, we designed and synthesized a library of
Lys-tagged peptides of a core length sufficient to span a bilayer
but with varying patterns of sequence, each composed of nine Leu residues,
nine Ser residues, and one (central) Trp residue. We found that peptides
containing contiguous Leu residues (Leu-block peptides, e.g., LLLLLLLLLWSSSSSSSSS),
in comparison to those containing discontinuous stretches of Leu residues
(non-Leu-block peptides, e.g., SLSLLSLSSWSLLSLSLLS),
displayed greater helicity (circular dichroism spectroscopy), traveled
slower during sodium dodecyl sulfate–polyacrylamide gel electrophoresis,
had longer reverse phase high-performance liquid chromatography retention
times on a C-18 column, and were helical when reconstituted into 1-palmitoyl-2-oleoylglycero-3-phosphocholine
liposomes, each observation indicating superior lipid compatibility
when a Leu-block is present. These parameters were largely paralleled
in a biological membrane insertion assay using microsomal membranes
from dog pancreas endoplasmic reticulum, where we found only the Leu-block
sequences successfully inserted; intriguingly, an amphipathic peptide
(SLLSSLLSSWLLSSLLSSL;
Leu face, Ser face) with biophysical properties similar to those of
Leu-block peptides failed to insert. Our overall results identify
local sequence lipid compatibility rather than average hydrophobicity
as a principal determinant of transmembrane segment potential, while
demonstrating that further subtleties of hydrophobic and helical patterning,
such as circumferential hydrophobicity in Leu-block segments, promote
translocon-mediated insertion.
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Affiliation(s)
- Tracy A Stone
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children , Toronto M5G 0A4, Ontario, Canada
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