1
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Nair AM, Jiang T, Mu B, Zhao R. Plastid Molecular Chaperone HSP90C Interacts with the SecA1 Subunit of Sec Translocase for Thylakoid Protein Transport. PLANTS (BASEL, SWITZERLAND) 2024; 13:1265. [PMID: 38732479 PMCID: PMC11085213 DOI: 10.3390/plants13091265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 04/24/2024] [Accepted: 04/29/2024] [Indexed: 05/13/2024]
Abstract
The plastid stroma-localized chaperone HSP90C plays a crucial role in maintaining optimal proteostasis within chloroplasts and participates in protein translocation processes. While existing studies have revealed HSP90C's direct interaction with the Sec translocase-dependent client pre-protein PsbO1 and the SecY1 subunit of the thylakoid membrane-bound Sec1 translocase channel system, its direct involvement with the extrinsic homodimeric Sec translocase subunit, SecA1, remains elusive. Employing bimolecular fluorescence complementation (BiFC) assay and other in vitro analyses, we unraveled potential interactions between HSP90C and SecA1. Our investigation revealed dynamic interactions between HSP90C and SecA1 at the thylakoid membrane and stroma. The thylakoid membrane localization of this interaction was contingent upon active HSP90C ATPase activity, whereas their stromal interaction was associated with active SecA1 ATPase activity. Furthermore, we observed a direct interaction between these two proteins by analyzing their ATP hydrolysis activities, and their interaction likely impacts their respective functional cycles. Additionally, using PsbO1, a model Sec translocase client pre-protein, we studied the intricacies of HSP90C's possible involvement in pre-protein translocation via the Sec1 system in chloroplasts. The results suggest a complex nature of the HSP90C-SecA1 interaction, possibly mediated by the Sec client protein. Our studies shed light on the nuanced aspects of HSP90C's engagement in orchestrating pre-protein translocation, and we propose a potential collaborative role of HSP90C with SecA1 in actively facilitating pre-protein transport across the thylakoid membrane.
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Affiliation(s)
| | | | | | - Rongmin Zhao
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada; Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; (A.M.N.); (T.J.); (B.M.)
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2
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Fiedler SM, Graumann PL. B. subtilis Sec and Srp Systems Show Dynamic Adaptations to Different Conditions of Protein Secretion. Cells 2024; 13:377. [PMID: 38474341 DOI: 10.3390/cells13050377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/04/2024] [Accepted: 02/16/2024] [Indexed: 03/14/2024] Open
Abstract
SecA is a widely conserved ATPase that drives the secretion of proteins across the cell membrane via the SecYEG translocon, while the SRP system is a key player in the insertion of membrane proteins via SecYEG. How SecA gains access to substrate proteins in Bacillus subtilis cells and copes with an increase in substrate availability during biotechnologically desired, high-level expression of secreted proteins is poorly understood. Using single molecule tracking, we found that SecA localization closely mimics that of ribosomes, and its molecule dynamics change similarly to those of ribosomes after inhibition of transcription or translation. These data suggest that B. subtilis SecA associates with signal peptides as they are synthesized at the ribosome, similar to the SRP system. In agreement with this, SecA is a largely mobile cytosolic protein; only a subset is statically associated with the cell membrane, i.e., likely with the Sec translocon. SecA dynamics were considerably different during the late exponential, transition, and stationary growth phases, revealing that single molecule dynamics considerably alter during different genetic programs in cells. During overproduction of a secretory protein, AmyE, SecA showed the strongest changes during the transition phase, i.e., where general protein secretion is high. To investigate whether the overproduction of AmyE also has an influence on other proteins that interact with SecYEG, we analyzed the dynamics of SecDF, YidC, and FtsY with and without AmyE overproduction. SecDF and YidC did not reveal considerable differences in single molecule dynamics during overexpression, while the SRP component FtsY changed markedly in its behavior and became more statically engaged. These findings indicate that the SRP pathway becomes involved in protein secretion upon an overload of proteins carrying a signal sequence. Thus, our data reveal high plasticity of the SecA and SRP systems in dealing with different needs for protein secretion.
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Affiliation(s)
- Svenja M Fiedler
- Fachbereich Chemie und Zentrum für Synthetische Mikrobiologie, SYNMIKRO, Philipps-Universität Marburg, Hans-Meerwein Straße 4, 35043 Marburg, Germany
| | - Peter L Graumann
- Fachbereich Chemie und Zentrum für Synthetische Mikrobiologie, SYNMIKRO, Philipps-Universität Marburg, Hans-Meerwein Straße 4, 35043 Marburg, Germany
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3
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Kefi M, Balabanidou V, Sarafoglou C, Charamis J, Lycett G, Ranson H, Gouridis G, Vontas J. ABCH2 transporter mediates deltamethrin uptake and toxicity in the malaria vector Anopheles coluzzii. PLoS Pathog 2023; 19:e1011226. [PMID: 37585450 PMCID: PMC10461823 DOI: 10.1371/journal.ppat.1011226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 08/28/2023] [Accepted: 07/28/2023] [Indexed: 08/18/2023] Open
Abstract
Contact insecticides are primarily used for the control of Anopheles malaria vectors. These chemicals penetrate mosquito legs and other appendages; the first barriers to reaching their neuronal targets. An ATP-Binding Cassette transporter from the H family (ABCH2) is highly expressed in Anopheles coluzzii legs, and further induced upon insecticide exposure. RNAi-mediated silencing of the ABCH2 caused a significant increase in deltamethrin mortality compared to control mosquitoes, coincident with a corresponding increase in 14C-deltamethrin penetration. RT-qPCR analysis and immunolocalization revealed ABCH2 to be mainly localized in the legs and head appendages, and more specifically, the apical part of the epidermis, underneath the cuticle. To unravel the molecular mechanism underlying the role of ABCH2 in modulating pyrethroid toxicity, two hypotheses were investigated: An indirect role, based on the orthology with other insect ABCH transporters involved with lipid transport and deposition of CHC lipids in Anopheles legs which may increase cuticle thickness, slowing down the penetration rate of deltamethrin; or the direct pumping of deltamethrin out of the organism. Evaluation of the leg cuticular hydrocarbon (CHC) content showed no affect by ABCH2 silencing, indicating this protein is not associated with the transport of leg CHCs. Homology-based modeling suggested that the ABCH2 half-transporter adopts a physiological homodimeric state, in line with its ability to hydrolyze ATP in vitro when expressed on its own in insect cells. Docking analysis revealed a deltamethrin pocket in the homodimeric transporter. Furthermore, deltamethrin-induced ATP hydrolysis in ABCH2-expressing cell membranes, further supports that deltamethrin is indeed an ABCH2 substrate. Overall, our findings pinpoint ABCH2 participating in deltamethrin toxicity regulation.
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Affiliation(s)
- Mary Kefi
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Vasileia Balabanidou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Chara Sarafoglou
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Jason Charamis
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Gareth Lycett
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Giorgos Gouridis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - John Vontas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
- Pesticide Science Laboratory, Department of Crop Science, Agricultural University of Athens, Athens, Greece
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4
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Atomic Force Microscopy Reveals Complexity Underlying General Secretory System Activity. Int J Mol Sci 2022; 24:ijms24010055. [PMID: 36613499 PMCID: PMC9820662 DOI: 10.3390/ijms24010055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/24/2022] Open
Abstract
The translocation of specific polypeptide chains across membranes is an essential activity for all life forms. The main components of the general secretory (Sec) system of E. coli include integral membrane translocon SecYEG, peripheral ATPase SecA, and SecDF, an ancillary complex that enhances polypeptide secretion by coupling translocation to proton motive force. Atomic force microscopy (AFM), a single-molecule imaging technique, is well suited to unmask complex, asynchronous molecular activities of membrane-associated proteins including those comprising the Sec apparatus. Using AFM, the dynamic structure of membrane-external protein topography of Sec system components can be directly visualized with high spatial-temporal precision. This mini-review is focused on AFM imaging of the Sec system in near-native fluid conditions where activity can be maintained and biochemically verified. Angstrom-scale conformational changes of SecYEG are reported on 100 ms timescales in fluid lipid bilayers. The association of SecA with SecYEG, forming membrane-bound SecYEG/SecA translocases, is directly visualized. Recent work showing topographical aspects of the translocation process that vary with precursor species is also discussed. The data suggests that the Sec system does not employ a single translocation mechanism. We posit that differences in the spatial frequency distribution of hydrophobic content within precursor sequences may be a determining factor in mechanism selection. Precise AFM investigations of active translocases are poised to advance our currently vague understanding of the complicated macromolecular movements underlying protein export across membranes.
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5
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Krishnamurthy S, Sardis MF, Eleftheriadis N, Chatzi KE, Smit JH, Karathanou K, Gouridis G, Portaliou AG, Bondar AN, Karamanou S, Economou A. Preproteins couple the intrinsic dynamics of SecA to its ATPase cycle to translocate via a catch and release mechanism. Cell Rep 2022; 38:110346. [PMID: 35139375 DOI: 10.1016/j.celrep.2022.110346] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 11/22/2021] [Accepted: 01/12/2022] [Indexed: 12/11/2022] Open
Abstract
Protein machines undergo conformational motions to interact with and manipulate polymeric substrates. The Sec translocase promiscuously recognizes, becomes activated, and secretes >500 non-folded preprotein clients across bacterial cytoplasmic membranes. Here, we reveal that the intrinsic dynamics of the translocase ATPase, SecA, and of preproteins combine to achieve translocation. SecA possesses an intrinsically dynamic preprotein clamp attached to an equally dynamic ATPase motor. Alternating motor conformations are finely controlled by the γ-phosphate of ATP, while ADP causes motor stalling, independently of clamp motions. Functional preproteins physically bridge these independent dynamics. Their signal peptides promote clamp closing; their mature domain overcomes the rate-limiting ADP release. While repeated ATP cycles shift the motor between unique states, multiple conformationally frustrated prongs in the clamp repeatedly "catch and release" trapped preprotein segments until translocation completion. This universal mechanism allows any preprotein to promiscuously recognize the translocase, usurp its intrinsic dynamics, and become secreted.
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Affiliation(s)
- Srinath Krishnamurthy
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Marios-Frantzeskos Sardis
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Nikolaos Eleftheriadis
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Katerina E Chatzi
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Jochem H Smit
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Konstantina Karathanou
- Freie Universität Berlin, Department of Physics, Theoretical Molecular Biophysics Group, Arnimallee 14, 14195 Berlin, Germany
| | - Giorgos Gouridis
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium; Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands; Structural Biology Division, Institute of Molecular Biology and Biotechnology (IMBB-FORTH), Nikolaou Plastira 100, Heraklion, Crete, Greece
| | - Athina G Portaliou
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Ana-Nicoleta Bondar
- Freie Universität Berlin, Department of Physics, Theoretical Molecular Biophysics Group, Arnimallee 14, 14195 Berlin, Germany; University of Bucharest, Faculty of Physics, Atomiștilor 405, 077125 Măgurele, Romania; Forschungszentrum Jülich, Institute of Computational Biomedicine, IAS-5/INM-9, Wilhelm-Johnen Straße, 5428 Jülich, Germany
| | - Spyridoula Karamanou
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium
| | - Anastassios Economou
- KU Leuven, University of Leuven, Rega Institute, Department of Microbiology and Immunology, 3000 Leuven, Belgium.
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6
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Thoma J, Burmann BM. Architects of their own environment: How membrane proteins shape the Gram-negative cell envelope. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:1-34. [PMID: 35034716 DOI: 10.1016/bs.apcsb.2021.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gram-negative bacteria are surrounded by a complex multilayered cell envelope, consisting of an inner and an outer membrane, and separated by the aqueous periplasm, which contains a thin peptidoglycan cell wall. These bacteria employ an arsenal of highly specialized membrane protein machineries to ensure the correct assembly and maintenance of the membranes forming the cell envelope. Here, we review the diverse protein systems, which perform these functions in Escherichia coli, such as the folding and insertion of membrane proteins, the transport of lipoproteins and lipopolysaccharide within the cell envelope, the targeting of phospholipids, and the regulation of mistargeted envelope components. Some of these protein machineries have been known for a long time, yet still hold surprises. Others have only recently been described and some are still missing pieces or yet remain to be discovered.
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Affiliation(s)
- Johannes Thoma
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden.
| | - Björn M Burmann
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
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7
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Davis MM, Lamichhane R, Bruce BD. Elucidating Protein Translocon Dynamics with Single-Molecule Precision. Trends Cell Biol 2021; 31:569-583. [PMID: 33865650 DOI: 10.1016/j.tcb.2021.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/28/2023]
Abstract
Translocons are protein assemblies that facilitate the targeting and transport of proteins into and across biological membranes. Our understanding of these systems has been advanced using genetics, biochemistry, and structural biology. Despite these classic advances, until recently we have still largely lacked a detailed understanding of how translocons recognize and facilitate protein translocation. With the advent and improvements of cryogenic electron microscopy (cryo-EM) single-particle analysis and single-molecule fluorescence microscopy, the details of how translocons function are finally emerging. Here, we introduce these methods and evaluate their importance in understanding translocon structure, function, and dynamics.
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Affiliation(s)
- Madeline M Davis
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
| | - Rajan Lamichhane
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
| | - Barry D Bruce
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Department of Microbiology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Graduate Program in Genome Science and Technology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Chemical and Biomolecular Engineering, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
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8
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Oswald J, Njenga R, Natriashvili A, Sarmah P, Koch HG. The Dynamic SecYEG Translocon. Front Mol Biosci 2021; 8:664241. [PMID: 33937339 PMCID: PMC8082313 DOI: 10.3389/fmolb.2021.664241] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 03/24/2021] [Indexed: 12/13/2022] Open
Abstract
The spatial and temporal coordination of protein transport is an essential cornerstone of the bacterial adaptation to different environmental conditions. By adjusting the protein composition of extra-cytosolic compartments, like the inner and outer membranes or the periplasmic space, protein transport mechanisms help shaping protein homeostasis in response to various metabolic cues. The universally conserved SecYEG translocon acts at the center of bacterial protein transport and mediates the translocation of newly synthesized proteins into and across the cytoplasmic membrane. The ability of the SecYEG translocon to transport an enormous variety of different substrates is in part determined by its ability to interact with multiple targeting factors, chaperones and accessory proteins. These interactions are crucial for the assisted passage of newly synthesized proteins from the cytosol into the different bacterial compartments. In this review, we summarize the current knowledge about SecYEG-mediated protein transport, primarily in the model organism Escherichia coli, and describe the dynamic interaction of the SecYEG translocon with its multiple partner proteins. We furthermore highlight how protein transport is regulated and explore recent developments in using the SecYEG translocon as an antimicrobial target.
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Affiliation(s)
- Julia Oswald
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin (ZMBZ), Faculty of Medicine, Albert Ludwigs Universität Freiburg, Freiburg, Germany
| | - Robert Njenga
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin (ZMBZ), Faculty of Medicine, Albert Ludwigs Universität Freiburg, Freiburg, Germany.,Faculty of Biology, Albert Ludwigs Universität Freiburg, Freiburg, Germany
| | - Ana Natriashvili
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin (ZMBZ), Faculty of Medicine, Albert Ludwigs Universität Freiburg, Freiburg, Germany.,Faculty of Biology, Albert Ludwigs Universität Freiburg, Freiburg, Germany
| | - Pinku Sarmah
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin (ZMBZ), Faculty of Medicine, Albert Ludwigs Universität Freiburg, Freiburg, Germany.,Faculty of Biology, Albert Ludwigs Universität Freiburg, Freiburg, Germany
| | - Hans-Georg Koch
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin (ZMBZ), Faculty of Medicine, Albert Ludwigs Universität Freiburg, Freiburg, Germany
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9
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A nexus of intrinsic dynamics underlies translocase priming. Structure 2021; 29:846-858.e7. [PMID: 33852897 DOI: 10.1016/j.str.2021.03.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/06/2021] [Accepted: 03/25/2021] [Indexed: 11/22/2022]
Abstract
The cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel assemble to form the Sec translocase. How this interaction primes and catalytically activates the translocase remains unclear. We show that priming exploits a nexus of intrinsic dynamics in SecA. Using atomistic simulations, smFRET, and HDX-MS, we reveal multiple dynamic islands that cross-talk with domain and quaternary motions. These dynamic elements are functionally important and conserved. Central to the nexus is a slender stem through which rotation of the preprotein clamp of SecA is biased by ATPase domain motions between open and closed clamping states. An H-bonded framework covering most of SecA enables multi-tier dynamics and conformational alterations with minimal energy input. As a result, cognate ligands select preexisting conformations and alter local dynamics to regulate catalytic activity and clamp motions. These events prime the translocase for high-affinity reception of non-folded preprotein clients. Dynamics nexuses are likely universal and essential in multi-liganded proteins.
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10
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Seinen AB, Spakman D, van Oijen AM, Driessen AJM. Cellular dynamics of the SecA ATPase at the single molecule level. Sci Rep 2021; 11:1433. [PMID: 33446830 PMCID: PMC7809386 DOI: 10.1038/s41598-021-81081-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 01/04/2021] [Indexed: 12/04/2022] Open
Abstract
In bacteria, the SecA ATPase provides the driving force for protein secretion via the SecYEG translocon. While the dynamic interplay between SecA and SecYEG in translocation is widely appreciated, it is not clear how SecA associates with the translocon in the crowded cellular environment. We use super-resolution microscopy to directly visualize the dynamics of SecA in Escherichia coli at the single-molecule level. We find that SecA is predominantly associated with and evenly distributed along the cytoplasmic membrane as a homodimer, with only a minor cytosolic fraction. SecA moves along the cell membrane as three distinct but interconvertible diffusional populations: (1) A state loosely associated with the membrane, (2) an integral membrane form, and (3) a temporarily immobile form. Disruption of the proton-motive-force, which is essential for protein secretion, re-localizes a significant portion of SecA to the cytoplasm and results in the transient location of SecA at specific locations at the membrane. The data support a model in which SecA diffuses along the membrane surface to gain access to the SecYEG translocon.
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Affiliation(s)
- Anne-Bart Seinen
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.,AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands
| | - Dian Spakman
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
| | | | - Arnold J M Driessen
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.
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11
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Roussel G, White SH. The SecA ATPase motor protein binds to Escherichia coli liposomes only as monomers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183358. [PMID: 32416191 DOI: 10.1016/j.bbamem.2020.183358] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 05/09/2020] [Accepted: 05/11/2020] [Indexed: 02/02/2023]
Abstract
The essential SecA motor ATPase acts in concert with the SecYEG translocon to secrete proteins into the periplasmic space of Escherichia coli. In aqueous solutions, SecA exists largely as dimers, but the oligomeric state on membranes is less certain. Crystallographic studies have suggested several possible solution dimeric states, but its oligomeric state when bound to membranes directly or indirectly via the translocon is controversial. We have shown using disulfide crosslinking that the principal solution dimer, corresponding to a crystallographic dimer (PDB 1M6N), binds only weakly to large unilamellar vesicles (LUV) formed from E. coli lipids. We report here that other soluble crosslinked crystallographic dimers also bind weakly, if at all, to LUV. Furthermore, using a simple glutaraldehyde crosslinking scheme, we show that SecA is always monomeric when bound to LUV formed from E. coli lipids.
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Affiliation(s)
- Guillaume Roussel
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA 92697, United States of America
| | - Stephen H White
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA 92697, United States of America.
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12
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Del Val C, Bondar AN. Diversity and sequence motifs of the bacterial SecA protein motor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183319. [PMID: 32335021 DOI: 10.1016/j.bbamem.2020.183319] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/17/2020] [Accepted: 04/19/2020] [Indexed: 12/24/2022]
Abstract
SecA is an essential component of the Sec protein secretion pathway in bacteria. Secretory proteins targeted to the Sec pathway by their N-terminal signal peptide bind to SecA, which couples binding and hydrolysis of adenosine triphosphate with movement of the secretory protein across the membrane-embedded SecYEG protein translocon. The phylogenetic diversity of bacteria raises the important question as to whether the region of SecA where the pre-protein binds has conserved sequence features that might impact the reaction mechanism of SecA. To address this question we established a large data set of SecA protein sequences and implemented a protocol to cluster and analyze these sequences according to features of two of the SecA functional domains, the protein binding domain and the nucleotide-binding domain 1. We identify remarkable sequence diversity of the protein binding domain, but also conserved motifs with potential role in protein binding. The N-terminus of SecA has sequence motifs that could help anchor SecA to the membrane. The overall sequence length and net estimated charge of SecA sequences depend on the organism.
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Affiliation(s)
- Coral Del Val
- University of Granada, Departmrent of Computer Science and Artificial Intelligence, E-18071 Granada, Spain; University of Granada, Andalusian Research Institute in Data Science and Computational Intelligence, E-18071 Granada, Spain.
| | - Ana-Nicoleta Bondar
- Freie Universität Berlin, Department of Physics, Theoretical Molecular Biophysics, D-14195 Berlin, Germany.
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13
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De Geyter J, Portaliou AG, Srinivasu B, Krishnamurthy S, Economou A, Karamanou S. Trigger factor is a bona fide secretory pathway chaperone that interacts with SecB and the translocase. EMBO Rep 2020; 21:e49054. [PMID: 32307852 DOI: 10.15252/embr.201949054] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 03/09/2020] [Accepted: 03/19/2020] [Indexed: 11/09/2022] Open
Abstract
Bacterial secretory preproteins are translocated across the inner membrane post-translationally by the SecYEG-SecA translocase. Mature domain features and signal peptides maintain preproteins in kinetically trapped, largely soluble, folding intermediates. Some aggregation-prone preproteins require chaperones, like trigger factor (TF) and SecB, for solubility and/or targeting. TF antagonizes the contribution of SecB to secretion by an unknown molecular mechanism. We reconstituted this interaction in vitro and studied targeting and secretion of the model preprotein pro-OmpA. TF and SecB display distinct, unsuspected roles in secretion. Tightly associating TF:pro-OmpA targets the translocase at SecA, but TF prevents pro-OmpA secretion. In solution, SecB binds TF:pro-OmpA with high affinity. At the membrane, when bound to the SecA C-tail, SecB increases TF and TF:pro-OmpA affinities for the translocase and allows pro-OmpA to resume translocation. Our data reveal that TF, a main cytoplasmic folding pathway chaperone, is also a bona fide post-translational secretory chaperone that directly interacts with both SecB and the translocase to mediate regulated protein secretion. Thus, TF links the cytoplasmic folding and secretion chaperone networks.
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Affiliation(s)
- Jozefien De Geyter
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Athina G Portaliou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Bindu Srinivasu
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Srinath Krishnamurthy
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Anastassios Economou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Spyridoula Karamanou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
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Cardiolipin is required in vivo for the stability of bacterial translocon and optimal membrane protein translocation and insertion. Sci Rep 2020; 10:6296. [PMID: 32286407 PMCID: PMC7156725 DOI: 10.1038/s41598-020-63280-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/25/2020] [Indexed: 01/05/2023] Open
Abstract
Translocation of preproteins across the Escherichia coli inner membrane requires anionic lipids by virtue of their negative head-group charge either in vivo or in situ. However, available results do not differentiate between the roles of monoanionic phosphatidylglycerol and dianionic cardiolipin (CL) in this essential membrane-related process. To define in vivo the molecular steps affected by the absence of CL in protein translocation and insertion, we analyzed translocon activity, SecYEG stability and its interaction with SecA in an E. coli mutant devoid of CL. Although no growth defects were observed, co- and post-translational translocation of α-helical proteins across inner membrane and the assembly of outer membrane β-barrel precursors were severely compromised in CL-lacking cells. Components of proton-motive force which could impair protein insertion into and translocation across the inner membrane, were unaffected. However, stability of the dimeric SecYEG complex and oligomerization properties of SecA were strongly compromised while the levels of individual SecYEG translocon components, SecA and insertase YidC were largely unaffected. These results demonstrate that CL is required in vivo for the stability of the bacterial translocon and its efficient function in co-translational insertion into and translocation across the inner membrane of E. coli.
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15
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Abstract
In bacteria, the Sec translocase mediates the translocation of proteins into and across the cytoplasmic membrane. It consists of a protein conducting channel SecYEG, the ATP-dependent motor SecA, and the accessory SecDF complex. Here we discuss the function and structure of the Sec translocase.
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16
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Abstract
More than a third of all bacterial polypeptides, comprising the 'exportome', are transported to extracytoplasmic locations. Most of the exportome is targeted and inserts into ('membranome') or crosses ('secretome') the plasma membrane. The membranome and secretome use distinct targeting signals and factors, and driving forces, but both use the ubiquitous and essential Sec translocase and its SecYEG protein-conducting channel. Membranome export is co-translational and uses highly hydrophobic N-terminal signal anchor sequences recognized by the signal recognition particle on the ribosome, that also targets C-tail anchor sequences. Translating ribosomes drive movement of these polypeptides through the lateral gate of SecY into the inner membrane. On the other hand, secretome export is post-translational and carries two types of targeting signals: cleavable N-terminal signal peptides and multiple short hydrophobic targeting signals in their mature domains. Secretome proteins remain translocation competent due to occupying loosely folded to completely non-folded states during targeting. This is accomplished mainly by the intrinsic properties of mature domains and assisted by signal peptides and/or chaperones. Secretome proteins bind to the dimeric SecA subunit of the translocase. SecA converts from a dimeric preprotein receptor to a monomeric ATPase motor and drives vectorial crossing of chains through SecY aided by the proton motive force. Signal peptides are removed by signal peptidases and translocated chains fold or follow subsequent trafficking.
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Abstract
The past several decades have witnessed tremendous growth in the protein targeting, transport and translocation field. Major advances were made during this time period. Now the molecular details of the targeting factors, receptors and the membrane channels that were envisioned in Blobel's Signal Hypothesis in the 1970s have been revealed by powerful structural methods. It is evident that there is a myriad of cytosolic and membrane associated systems that accurately sort and target newly synthesized proteins to their correct membrane translocases for membrane insertion or protein translocation. Here we will describe the common principles for protein transport in prokaryotes and eukaryotes.
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Novel Sequence Feature of SecA Translocase Protein Unique to the Thermophilic Bacteria: Bioinformatics Analyses to Investigate Their Potential Roles. Microorganisms 2019; 8:microorganisms8010059. [PMID: 31905784 PMCID: PMC7023208 DOI: 10.3390/microorganisms8010059] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 12/24/2019] [Accepted: 12/25/2019] [Indexed: 11/25/2022] Open
Abstract
SecA is an evolutionarily conserved protein that plays an indispensable role in the secretion of proteins across the bacterial cell membrane. Comparative analyses of SecA homologs have identified two large conserved signature inserts (CSIs) that are unique characteristics of thermophilic bacteria. A 50 aa conserved insert in SecA is exclusively present in the SecA homologs from the orders Thermotogales and Aquificales, while a 76 aa insert in SecA is specific for the order Thermales and Hydrogenibacillus schlegelii. Phylogenetic analyses on SecA sequences show that the shared presence of these CSIs in unrelated groups of thermophiles is not due to lateral gene transfers, but instead these large CSIs have likely originated independently in these lineages due to their advantageous function. Both of these CSIs are located in SecA protein in a surface exposed region within the ATPase domain. To gain insights into the functional significance of the 50 aa CSI in SecA, molecular dynamics (MD) simulations were performed at two different temperatures using ADP-bound SecA from Thermotoga maritima. These analyses have identified a conserved network of water molecules near the 50 aa insert in which the Glu185 residue from the CSI is found to play a key role towards stabilizing these interactions. The results provide evidence for the possible role of the 50 aa CSI in stabilizing the binding interaction of ADP/ATP, which is required for SecA function. Additionally, the surface-exposed CSIs in SecA, due to their potential to make novel protein-protein interactions, could also contribute to the thermostability of SecA from thermophilic bacteria.
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Roussel G, White SH. Binding of SecA ATPase monomers and dimers to lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183112. [PMID: 31676370 DOI: 10.1016/j.bbamem.2019.183112] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/01/2019] [Accepted: 10/03/2019] [Indexed: 11/29/2022]
Abstract
The Escherichia coli SecA ATPase motor protein is essential for secretion of proteins through the SecYEG translocon into the periplasmic space. Its function relies upon interactions with the surrounding lipid bilayer as well as SecYEG translocon. That negatively charged lipids are required for bilayer binding has been known for >25 years, but little systematic quantitative data is available. We have carried out an extensive investigation of SecA partitioning into large unilamellar vesicles (LUV) using a wide range of lipid and electrolyte compositions, including the principal cytoplasmic salt of E. coli, potassium glutamate, which we have shown stabilizes SecA. The water-to-bilayer transfer free energy is about -7.5 kcal mol-1 for typical E. coli lipid compositions. Although it has been established that SecA is dimeric in the cytoplasm, we find that the most widely cited dimer form (PDB 1M6N) binds only weakly to LUVs formed from E. coli lipids.
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Affiliation(s)
- Guillaume Roussel
- Department of Physiology & Biophysics, University of California, Irvine, CA 92697, United States of America
| | - Stephen H White
- Department of Physiology & Biophysics, University of California, Irvine, CA 92697, United States of America.
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20
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Cranford-Smith T, Huber D. The way is the goal: how SecA transports proteins across the cytoplasmic membrane in bacteria. FEMS Microbiol Lett 2019; 365:4969678. [PMID: 29790985 PMCID: PMC5963308 DOI: 10.1093/femsle/fny093] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/10/2018] [Indexed: 02/06/2023] Open
Abstract
In bacteria, translocation of most soluble secreted proteins (and outer membrane proteins in Gram-negative bacteria) across the cytoplasmic membrane by the Sec machinery is mediated by the essential ATPase SecA. At its core, this machinery consists of SecA and the integral membrane proteins SecYEG, which form a protein conducting channel in the membrane. Proteins are recognised by the Sec machinery by virtue of an internally encoded targeting signal, which usually takes the form of an N-terminal signal sequence. In addition, substrate proteins must be maintained in an unfolded conformation in the cytoplasm, prior to translocation, in order to be competent for translocation through SecYEG. Recognition of substrate proteins occurs via SecA—either through direct recognition by SecA or through secondary recognition by a molecular chaperone that delivers proteins to SecA. Substrate proteins are then screened for the presence of a functional signal sequence by SecYEG. Proteins with functional signal sequences are translocated across the membrane in an ATP-dependent fashion. The current research investigating each of these steps is reviewed here.
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Affiliation(s)
- Tamar Cranford-Smith
- Institute for Microbiology and Infection School of Biosciences University of Birmingham Edgbaston Birmingham B15 2TT, UK
| | - Damon Huber
- Institute for Microbiology and Infection School of Biosciences University of Birmingham Edgbaston Birmingham B15 2TT, UK
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21
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Abstract
Bacterial protein transport via the conserved SecYEG translocon is generally classified as either cotranslational, i.e., when transport is coupled to translation, or posttranslational, when translation and transport are separated. We show here that the ATPase SecA, which is considered to bind its substrates posttranslationally, already scans the ribosomal tunnel for potential substrates. In the presence of a nascent chain, SecA retracts from the tunnel but maintains contact with the ribosomal surface. This is remarkably similar to the ribosome-binding mode of the signal recognition particle, which mediates cotranslational transport. Our data reveal a striking plasticity of protein transport pathways, which likely enable bacteria to efficiently recognize and transport a large number of highly different substrates within their short generation time. Bacteria execute a variety of protein transport systems for maintaining the proper composition of their different cellular compartments. The SecYEG translocon serves as primary transport channel and is engaged in transporting two different substrate types. Inner membrane proteins are cotranslationally inserted into the membrane after their targeting by the signal recognition particle (SRP). In contrast, secretory proteins are posttranslationally translocated by the ATPase SecA. Recent data indicate that SecA can also bind to ribosomes close to the tunnel exit. We have mapped the interaction of SecA with translating and nontranslating ribosomes and demonstrate that the N terminus and the helical linker domain of SecA bind to an acidic patch on the surface of the ribosomal protein uL23. Intriguingly, both also insert deeply into the ribosomal tunnel to contact the intratunnel loop of uL23, which serves as a nascent chain sensor. This binding pattern is remarkably similar to that of SRP and indicates an identical interaction mode of the two targeting factors with ribosomes. In the presence of a nascent chain, SecA retracts from the tunnel but maintains contact with the surface of uL23. Our data further demonstrate that ribosome and membrane binding of SecA are mutually exclusive, as both events depend on the N terminus of SecA. Our study highlights the enormous plasticity of bacterial protein transport systems and reveals that the discrimination between SRP and SecA substrates is already initiated at the ribosome.
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22
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Sanganna Gari RR, Chattrakun K, Marsh BP, Mao C, Chada N, Randall LL, King GM. Direct visualization of the E. coli Sec translocase engaging precursor proteins in lipid bilayers. SCIENCE ADVANCES 2019; 5:eaav9404. [PMID: 31206019 PMCID: PMC6561738 DOI: 10.1126/sciadv.aav9404] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 05/09/2019] [Indexed: 06/09/2023]
Abstract
Escherichia coli exports proteins via a translocase comprising SecA and the translocon, SecYEG. Structural changes of active translocases underlie general secretory system function, yet directly visualizing dynamics has been challenging. We imaged active translocases in lipid bilayers as a function of precursor protein species, nucleotide species, and stage of translocation using atomic force microscopy (AFM). Starting from nearly identical initial states, SecA more readily dissociated from SecYEG when engaged with the precursor of outer membrane protein A as compared to the precursor of galactose-binding protein. For the SecA that remained bound to the translocon, the quaternary structure varied with nucleotide, populating SecA2 primarily with adenosine diphosphate (ADP) and adenosine triphosphate, and the SecA monomer with the transition state analog ADP-AlF3. Conformations of translocases exhibited precursor-dependent differences on the AFM imaging time scale. The data, acquired under near-native conditions, suggest that the translocation process varies with precursor species.
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Affiliation(s)
| | - Kanokporn Chattrakun
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Brendan P. Marsh
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Chunfeng Mao
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Nagaraju Chada
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Gavin M. King
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
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23
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Young J, Duong F. Investigating the stability of the SecA-SecYEG complex during protein translocation across the bacterial membrane. J Biol Chem 2019; 294:3577-3587. [PMID: 30602566 DOI: 10.1074/jbc.ra118.006447] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 12/21/2018] [Indexed: 11/06/2022] Open
Abstract
During posttranslational translocation in Escherichia coli, polypeptide substrates are driven across the membrane through the SecYEG protein-conducting channel using the ATPase SecA, which binds to SecYEG and couples nucleotide hydrolysis to polypeptide movement. Recent studies suggest that SecA is a highly dynamic enzyme, able to repeatedly bind and dissociate from SecYEG during substrate translocation, but other studies indicate that these dynamics, here referred to as "SecA processivity," are not a requirement for transport. We employ a SecA mutant (PrlD23) that associates more tightly to membranes than WT SecA, in addition to a SecA-SecYEG cross-linked complex, to demonstrate that SecA-SecYEG binding and dissociation events are important for efficient transport of the periplasmic protein proPhoA. Strikingly however, we find that transport of the precursor of the outer membrane protein proOmpA does not depend on SecA processivity. By exchanging signal sequence and protein domains of similar size between PhoA and OmpA, we find that SecA processivity is not influenced by the sequence of the protein substrate. In contrast, using an extended proOmpA variant and a truncated derivative of proPhoA, we show that SecA processivity is affected by substrate length. These findings underscore the importance of the dynamic nature of SecA-SecYEG interactions as a function of the preprotein substrate, features that have not yet been reported using other biophysical or in vivo methods.
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Affiliation(s)
- John Young
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Franck Duong
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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24
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Abstract
The inner membrane of Gram-negative bacteria is a ~6 nm thick phospholipid bilayer. It forms a semi-permeable barrier between the cytoplasm and periplasm allowing only regulated export and import of ions, sugar polymers, DNA and proteins. Inner membrane proteins, embedded via hydrophobic transmembrane α-helices, play an essential role in this regulated trafficking: they mediate insertion into the membrane (insertases) or complete crossing of the membrane (translocases) or both. The Gram-negative inner membrane is equipped with a variety of different insertases and translocases. Many of them are specialized, taking care of the export of only a few protein substrates, while others have more general roles. Here, we focus on the three general export/insertion pathways, the secretory (Sec) pathway, YidC and the twin-arginine translocation (TAT) pathway, focusing closely on the Escherichia coli (E. coli) paradigm. We only briefly mention dedicated export pathways found in different Gram-negative bacteria. The Sec system deals with the majority of exported proteins and functions both as a translocase for secretory proteins and an insertase for membrane proteins. The insertase YidC assists the Sec system or operates independently on membrane protein clients. Sec and YidC, in common with most export pathways, require their protein clients to be in soluble non-folded states to fit through the translocation channels and grooves. The TAT pathway is an exception, as it translocates folded proteins, some loaded with prosthetic groups.
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Affiliation(s)
- Jozefien De Geyter
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Dries Smets
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium.
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25
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Vandenberk N, Karamanou S, Portaliou AG, Zorzini V, Hofkens J, Hendrix J, Economou A. The Preprotein Binding Domain of SecA Displays Intrinsic Rotational Dynamics. Structure 2018; 27:90-101.e6. [PMID: 30471924 DOI: 10.1016/j.str.2018.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 08/27/2018] [Accepted: 10/10/2018] [Indexed: 11/26/2022]
Abstract
SecA converts ATP energy to protein translocation work. Together with the membrane-embedded SecY channel it forms the bacterial protein translocase. How secretory proteins bind to SecA and drive conformational cascades to promote their secretion remains unknown. To address this, we focus on the preprotein binding domain (PBD) of SecA. PBD crystalizes in three distinct states, swiveling around its narrow stem. Here, we examined whether PBD displays intrinsic dynamics in solution using single-molecule Förster resonance energy transfer (smFRET). Unique cysteinyl pairs on PBD and apposed domains were labeled with donor/acceptor dyes. Derivatives were analyzed using pulsed interleaved excitation and multi-parameter fluorescence detection. The PBD undergoes significant rotational motions, occupying at least three distinct states in dimeric and four in monomeric soluble SecA. Nucleotides do not affect smFRET-detectable PBD dynamics. These findings lay the foundations for single-molecule dissection of translocase mechanics and suggest models for possible PBD involvement during catalysis.
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Affiliation(s)
- Niels Vandenberk
- KU Leuven, Department of Chemistry, Division for Molecular Imaging and Photonics, Laboratory for Photochemistry and Spectroscopy, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Spyridoula Karamanou
- KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory for Molecular Bacteriology, Herestraat 49, Gasthuisberg Campus, B-3000 Leuven, Belgium
| | - Athina G Portaliou
- KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory for Molecular Bacteriology, Herestraat 49, Gasthuisberg Campus, B-3000 Leuven, Belgium
| | - Valentina Zorzini
- KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory for Molecular Bacteriology, Herestraat 49, Gasthuisberg Campus, B-3000 Leuven, Belgium
| | - Johan Hofkens
- KU Leuven, Department of Chemistry, Division for Molecular Imaging and Photonics, Laboratory for Photochemistry and Spectroscopy, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Jelle Hendrix
- KU Leuven, Department of Chemistry, Division for Molecular Imaging and Photonics, Laboratory for Photochemistry and Spectroscopy, Celestijnenlaan 200F, B-3001 Leuven, Belgium; Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), Hasselt University, B-3590 Diepenbeek, Belgium.
| | - Anastassios Economou
- KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory for Molecular Bacteriology, Herestraat 49, Gasthuisberg Campus, B-3000 Leuven, Belgium.
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26
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Chada N, Chattrakun K, Marsh BP, Mao C, Bariya P, King GM. Single-molecule observation of nucleotide induced conformational changes in basal SecA-ATP hydrolysis. SCIENCE ADVANCES 2018; 4:eaat8797. [PMID: 30397644 PMCID: PMC6200364 DOI: 10.1126/sciadv.aat8797] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/13/2018] [Indexed: 05/06/2023]
Abstract
SecA is the critical adenosine triphosphatase that drives preprotein transport through the translocon, SecYEG, in Escherichia coli. This process is thought to be regulated by conformational changes of specific domains of SecA, but real-time, real-space measurement of these changes is lacking. We use single-molecule atomic force microscopy (AFM) to visualize nucleotide-dependent conformations and conformational dynamics of SecA. Distinct topographical populations were observed in the presence of specific nucleotides. AFM investigations during basal adenosine triphosphate (ATP) hydrolysis revealed rapid, reversible transitions between a compact and an extended state at the ~100-ms time scale. A SecA mutant lacking the precursor-binding domain (PBD) aided interpretation. Further, the biochemical activity of SecA prepared for AFM was confirmed by tracking inorganic phosphate release. We conclude that ATP-driven dynamics are largely due to PBD motion but that other segments of SecA contribute to this motion during the transition state of the ATP hydrolysis cycle.
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Affiliation(s)
- Nagaraju Chada
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Kanokporn Chattrakun
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Brendan P. Marsh
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Chunfeng Mao
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Priya Bariya
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Gavin M. King
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
- Corresponding author.
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27
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Knyazev DG, Kuttner R, Zimmermann M, Sobakinskaya E, Pohl P. Driving Forces of Translocation Through Bacterial Translocon SecYEG. J Membr Biol 2018; 251:329-343. [PMID: 29330604 PMCID: PMC6028853 DOI: 10.1007/s00232-017-0012-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Accepted: 12/22/2017] [Indexed: 11/09/2022]
Abstract
This review focusses on the energetics of protein translocation via the Sec translocation machinery. First we complement structural data about SecYEG's conformational rearrangements by insight obtained from functional assays. These include measurements of SecYEG permeability that allow assessment of channel gating by ligand binding and membrane voltage. Second we will discuss the power stroke and Brownian ratcheting models of substrate translocation and the role that the two models assign to the putative driving forces: (i) ATP (SecA) and GTP (ribosome) hydrolysis, (ii) interaction with accessory proteins, (iii) membrane partitioning and folding, (iv) proton motive force (PMF), and (v) entropic contributions. Our analysis underlines how important energized membranes are for unravelling the translocation mechanism in future experiments.
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Affiliation(s)
- Denis G Knyazev
- Johannes Kepler University Linz, Institute of Biophysics, Linz, Austria.
| | - Roland Kuttner
- Johannes Kepler University Linz, Institute of Biophysics, Linz, Austria
| | - Mirjam Zimmermann
- Johannes Kepler University Linz, Institute of Biophysics, Linz, Austria
| | | | - Peter Pohl
- Johannes Kepler University Linz, Institute of Biophysics, Linz, Austria
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28
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Motions of the SecA protein motor bound to signal peptide: Insights from molecular dynamics simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:416-427. [DOI: 10.1016/j.bbamem.2017.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 11/03/2017] [Accepted: 11/07/2017] [Indexed: 12/31/2022]
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29
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Hamed MB, Karamanou S, Ólafsdottir S, Basílio JSM, Simoens K, Tsolis KC, Van Mellaert L, Guðmundsdóttir EE, Hreggvidsson GO, Anné J, Bernaerts K, Fridjonsson OH, Economou A. Large-scale production of a thermostable Rhodothermus marinus cellulase by heterologous secretion from Streptomyces lividans. Microb Cell Fact 2017; 16:232. [PMID: 29274637 PMCID: PMC5741968 DOI: 10.1186/s12934-017-0847-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/13/2017] [Indexed: 01/28/2023] Open
Abstract
Background The gene encoding a thermostable cellulase of family 12 was previously isolated from a Rhodothermus marinus through functional screening. CelA is a protein of 260 aminoacyl residues with a 28-residue amino-terminal signal peptide. Mature CelA was poorly synthesized in some Escherichia coli strains and not at all in others. Here we present an alternative approach for its heterologous production as a secreted polypeptide in Streptomyces. Results CelA was successfully over-expressed as a secreted polypeptide in Streptomyces lividans TK24. To this end, CelA was fused C-terminally to the secretory signal peptide of the subtilisin inhibitor protein (Sianidis et al. in J Biotechnol. 121: 498–507, 2006) from Streptomyces venezuelae and a new cloning strategy developed. Optimal growth media and conditions that stall biomass production promote excessive CelA secretion. Under optimal growth conditions in nutrient broth medium, significant amounts of mature CelA (50–90 mg/L or 100–120 mg/g of dry cell weight) are secreted in the spent growth media after 7 days. A protocol to rapidly purify CelA to homogeneity from culture supernatants was developed and specific anti-sera raised against it. Biophysical, biochemical and immmuno-detection analyses indicate that the enzyme is intact, stable and fully functional. CelA is the most thermostable heterologous polypeptide shown to be secreted from S. lividans. Conclusion This study further validates and extends the use of the S. lividans platform for production of heterologous enzymes of industrial importance and extends it to active thermostable enzymes. This study contributes to developing a platform for poly-omics analysis of protein secretion in S. lividans. Electronic supplementary material The online version of this article (10.1186/s12934-017-0847-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mohamed Belal Hamed
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium.,Department of Molecular Biology, National Research Centre, Dokki, Giza, Egypt
| | - Spyridoula Karamanou
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium
| | | | - Joana Sofia Martins Basílio
- Bio- & Chemical Systems Technology, Reactor Engineering and Safety Section, Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Louvain, Belgium
| | - Kenneth Simoens
- Bio- & Chemical Systems Technology, Reactor Engineering and Safety Section, Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Louvain, Belgium
| | - Kostantinos C Tsolis
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium
| | - Lieve Van Mellaert
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium
| | | | | | - Jozef Anné
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium
| | - Kristel Bernaerts
- Bio- & Chemical Systems Technology, Reactor Engineering and Safety Section, Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Louvain, Belgium
| | | | - Anastassios Economou
- Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000, Louvain, Belgium.
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Portaliou AG, Tsolis KC, Loos MS, Balabanidou V, Rayo J, Tsirigotaki A, Crepin VF, Frankel G, Kalodimos CG, Karamanou S, Economou A. Hierarchical protein targeting and secretion is controlled by an affinity switch in the type III secretion system of enteropathogenic Escherichia coli. EMBO J 2017; 36:3517-3531. [PMID: 29109154 DOI: 10.15252/embj.201797515] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/05/2017] [Accepted: 10/11/2017] [Indexed: 11/09/2022] Open
Abstract
Type III secretion (T3S), a protein export pathway common to Gram-negative pathogens, comprises a trans-envelope syringe, the injectisome, with a cytoplasm-facing translocase channel. Exported substrates are chaperone-delivered to the translocase, EscV in enteropathogenic Escherichia coli, and cross it in strict hierarchical manner, for example, first "translocators", then "effectors". We dissected T3S substrate targeting and hierarchical switching by reconstituting them in vitro using inverted inner membrane vesicles. EscV recruits and conformationally activates the tightly membrane-associated pseudo-effector SepL and its chaperone SepD. This renders SepL a high-affinity receptor for translocator/chaperone pairs, recognizing specific chaperone signals. In a second, SepD-coupled step, translocators docked on SepL become secreted. During translocator secretion, SepL/SepD suppress effector/chaperone binding to EscV and prevent premature effector secretion. Disengagement of the SepL/SepD switch directs EscV to dedicated effector export. These findings advance molecular understanding of T3S and reveal a novel mechanism for hierarchical trafficking regulation in protein secretion channels.
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Affiliation(s)
- Athina G Portaliou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Konstantinos C Tsolis
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Maria S Loos
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Vassileia Balabanidou
- Institute of Molecular Biology and Biotechnology, FORTH (Foundation of Research and Technology), University of Crete, Heraklion, Greece
| | - Josep Rayo
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Alexandra Tsirigotaki
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Valerie F Crepin
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Gad Frankel
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | | | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
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31
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Yazdi AK, Vezina GC, Shilton BH. An alternate mode of oligomerization for E. coli SecA. Sci Rep 2017; 7:11747. [PMID: 28924213 PMCID: PMC5603524 DOI: 10.1038/s41598-017-11648-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 08/29/2017] [Indexed: 11/08/2022] Open
Abstract
SecA is the ATPase of preprotein translocase. SecA is a dimer in solution and changes in its oligomeric state may function in preprotein translocation. The SecA-N68 construct, in which the C-terminal helical domains of SecA are deleted, was used to investigate the mechanism of SecA oligomerization. SecA-N68 is in equilibrium between monomers, dimers, and tetramers. Subunit interactions in the SecA-N68 tetramer are mediated entirely by unstructured regions at its N- and C-termini: when the termini are deleted to yield SecA-N68∆NC, the construct is completely monomeric. This monomeric construct yielded crystals diffracting to 2.6 Å that were used to solve the structure of SecA-N68, including the "preprotein crosslinking domain" (PPXD) that was missing from previous E. coli SecA structures. The SecA-N68 structure was combined with small angle X-ray scattering (SAXS) data to construct a model of the SecA-N68 tetramer that is consistent with the essential roles of the extreme N- and C-termini in oligomerization. This mode of oligomerization, which depends on binding of the extreme N-terminus to the DEAD motor domains, NBD1 and NBD2, was used to model a novel parallel and flexible SecA solution dimer that agrees well with SAXS data.
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Affiliation(s)
- Aliakbar Khalili Yazdi
- Department of Biochemistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Grant C Vezina
- Department of Biochemistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Brian H Shilton
- Department of Biochemistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
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Abstract
We came together in Leeds to commemorate and celebrate the life and achievements of Prof. Stephen Baldwin. For many years we, together with Sheena Radford and Roman Tuma (colleagues also of the University of Leeds), have worked together on the problem of protein translocation through the essential and ubiquitous Sec system. Inspired and helped by Steve we may finally be making progress. My seminar described our latest hypothesis for the molecular mechanism of protein translocation, supported by results collected in Bristol and Leeds on the tractable bacterial secretion process–commonly known as the Sec system; work that will be published elsewhere. Below is a description of the alternative and contested models for protein translocation that we all have been contemplating for many years. This review will consider their pros and cons.
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Sardis MF, Tsirigotaki A, Chatzi KE, Portaliou AG, Gouridis G, Karamanou S, Economou A. Preprotein Conformational Dynamics Drive Bivalent Translocase Docking and Secretion. Structure 2017. [DOI: 10.1016/j.str.2017.05.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Chatzi KE, Sardis MF, Tsirigotaki A, Koukaki M, Šoštarić N, Konijnenberg A, Sobott F, Kalodimos CG, Karamanou S, Economou A. Preprotein mature domains contain translocase targeting signals that are essential for secretion. J Cell Biol 2017; 216:1357-1369. [PMID: 28404644 PMCID: PMC5412566 DOI: 10.1083/jcb.201609022] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 10/07/2016] [Accepted: 02/23/2017] [Indexed: 11/22/2022] Open
Abstract
Secretory proteins are only temporary cytoplasmic residents. They are typically synthesized as preproteins, carrying signal peptides N-terminally fused to their mature domains. In bacteria secretion largely occurs posttranslationally through the membrane-embedded SecA-SecYEG translocase. Upon crossing the plasma membrane, signal peptides are cleaved off and mature domains reach their destinations and fold. Targeting to the translocase is mediated by signal peptides. The role of mature domains in targeting and secretion is unclear. We now reveal that mature domains harbor their own independent targeting signals (mature domain targeting signals [MTSs]). These are multiple, degenerate, interchangeable, linear or 3D hydrophobic stretches that become available because of the unstructured states of targeting-competent preproteins. Their receptor site on the cytoplasmic face of the SecYEG-bound SecA is also of hydrophobic nature and is located adjacent to the signal peptide cleft. Both the preprotein MTSs and their receptor site on SecA are essential for protein secretion. Evidently, mature domains have their own previously unsuspected distinct roles in preprotein targeting and secretion.
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Affiliation(s)
- Katerina E Chatzi
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Marios Frantzeskos Sardis
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Alexandra Tsirigotaki
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Marina Koukaki
- Institute of Molecular Biology and Biotechnology FoRTH, Iraklio, 71110 Crete, Greece
| | - Nikolina Šoštarić
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Albert Konijnenberg
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, 2000 Antwerp, Belgium
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, 2000 Antwerp, Belgium
| | - Charalampos G Kalodimos
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium .,Institute of Molecular Biology and Biotechnology FoRTH, Iraklio, 71110 Crete, Greece
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35
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Banerjee T, Lindenthal C, Oliver D. SecA functions in vivo as a discrete anti-parallel dimer to promote protein transport. Mol Microbiol 2016; 103:439-451. [PMID: 27802584 DOI: 10.1111/mmi.13567] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2016] [Indexed: 01/28/2023]
Abstract
SecA ATPase motor protein plays a central role in bacterial protein transport by binding substrate proteins and the SecY channel complex and utilizing its ATPase activity to drive protein translocation across the plasma membrane. SecA has been shown to exist in a dynamic monomer-dimer equilibrium modulated by translocation ligands, and multiple structural forms of the dimer have been crystallized. Since the structural form of the dimer remains a controversial and unresolved question, we addressed this matter by engineering ρ-benzoylphenylalanine along dimer interfaces corresponding to the five different SecA X-ray structures and assessing their in vivo photo-crosslinking pattern. A discrete anti-parallel 1M6N-like dimer was the dominant if not exclusive dimer found in vivo, whether SecA was cytosolic or in lipid or SecYEG-bound states. SecA bound to a stable translocation intermediate was crosslinked in vivo to a second SecA protomer at its 1M6N interface, suggesting that this specific dimer likely promotes active protein translocation. Taken together, our studies strengthen models that posit, at least in part, a SecA dimer-driven translocation mechanism.
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Affiliation(s)
- Tithi Banerjee
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT, 06459, USA
| | - Christine Lindenthal
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT, 06459, USA
| | - Donald Oliver
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT, 06459, USA
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37
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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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38
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Prabudiansyah I, Driessen AJM. The Canonical and Accessory Sec System of Gram-positive Bacteria. Curr Top Microbiol Immunol 2016; 404:45-67. [DOI: 10.1007/82_2016_9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Structural Similarities and Differences between Two Functionally Distinct SecA Proteins, Mycobacterium tuberculosis SecA1 and SecA2. J Bacteriol 2015; 198:720-30. [PMID: 26668263 DOI: 10.1128/jb.00696-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 12/01/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED While SecA is the ATPase component of the major bacterial secretory (Sec) system, mycobacteria and some Gram-positive pathogens have a second paralog, SecA2. In bacteria with two SecA paralogs, each SecA is functionally distinct, and they cannot compensate for one another. Compared to SecA1, SecA2 exports a distinct and smaller set of substrates, some of which have roles in virulence. In the mycobacterial system, some SecA2-dependent substrates lack a signal peptide, while others contain a signal peptide but possess features in the mature protein that necessitate a role for SecA2 in their export. It is unclear how SecA2 functions in protein export, and one open question is whether SecA2 works with the canonical SecYEG channel to export proteins. In this study, we report the structure of Mycobacterium tuberculosis SecA2 (MtbSecA2), which is the first structure of any SecA2 protein. A high level of structural similarity is observed between SecA2 and SecA1. The major structural difference is the absence of the helical wing domain, which is likely to play a role in how MtbSecA2 recognizes its unique substrates. Importantly, structural features critical to the interaction between SecA1 and SecYEG are preserved in SecA2. Furthermore, suppressor mutations of a dominant-negative secA2 mutant map to the surface of SecA2 and help identify functional regions of SecA2 that may promote interactions with SecYEG or the translocating polypeptide substrate. These results support a model in which the mycobacterial SecA2 works with SecYEG. IMPORTANCE SecA2 is a paralog of SecA1, which is the ATPase of the canonical bacterial Sec secretion system. SecA2 has a nonredundant function with SecA1, and SecA2 exports a distinct and smaller set of substrates than SecA1. This work reports the crystal structure of SecA2 of Mycobacterium tuberculosis (the first SecA2 structure reported for any organism). Many of the structural features of SecA1 are conserved in the SecA2 structure, including putative contacts with the SecYEG channel. Several structural differences are also identified that could relate to the unique function and selectivity of SecA2. Suppressor mutations of a secA2 mutant map to the surface of SecA2 and help identify functional regions of SecA2 that may promote interactions with SecYEG.
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40
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Papanastasiou M, Orfanoudaki G, Kountourakis N, Koukaki M, Sardis MF, Aivaliotis M, Tsolis KC, Karamanou S, Economou A. Rapid label-free quantitative analysis of the E. coli
BL21(DE3) inner membrane proteome. Proteomics 2015; 16:85-97. [DOI: 10.1002/pmic.201500304] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 09/05/2015] [Accepted: 10/12/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Malvina Papanastasiou
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Department Pathology & Laboratory Medicine, Perelman School of Medicine; University of Pennsylvania; Philadelphia USA
| | - Georgia Orfanoudaki
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Department of Biology; University of Crete; Iraklio Greece
| | - Nikos Kountourakis
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
| | - Marina Koukaki
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
| | - Marios Frantzeskos Sardis
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology; Katholieke Universiteit Leuven; Leuven Belgium
| | - Michalis Aivaliotis
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
| | - Konstantinos C. Tsolis
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Department of Biology; University of Crete; Iraklio Greece
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology; Katholieke Universiteit Leuven; Leuven Belgium
| | - Spyridoula Karamanou
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology; Katholieke Universiteit Leuven; Leuven Belgium
| | - Anastassios Economou
- Institute of Molecular Biology and Biotechnology; Foundation for Research & Technology; Iraklio Greece
- Department of Biology; University of Crete; Iraklio Greece
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology; Katholieke Universiteit Leuven; Leuven Belgium
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41
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In Vitro Interaction of the Housekeeping SecA1 with the Accessory SecA2 Protein of Mycobacterium tuberculosis. PLoS One 2015; 10:e0128788. [PMID: 26047312 PMCID: PMC4457860 DOI: 10.1371/journal.pone.0128788] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/30/2015] [Indexed: 12/22/2022] Open
Abstract
The majority of proteins that are secreted across the bacterial cytoplasmic membrane leave the cell via the Sec pathway, which in its minimal form consists of the dimeric ATP-driven motor protein SecA that associates with the protein-conducting membrane pore SecYEG. Some Gram-positive bacteria contain two homologues of SecA, termed SecA1 and SecA2. SecA1 is the essential housekeeping protein, whereas SecA2 is not essential but is involved in the translocation of a subset of proteins, including various virulence factors. Some SecA2 containing bacteria also harbor a homologous SecY2 protein that may form a separate translocase. Interestingly, mycobacteria contain only one SecY protein and thus both SecA1 and SecA2 are required to interact with SecYEG, either individually or together as a heterodimer. In order to address whether SecA1 and SecA2 cooperate during secretion of SecA2 dependent proteins, we examined the oligomeric state of SecA1 and SecA2 of Mycobacterium tuberculosis and their interactions with SecA2 and the cognate SecA1, respectively. We conclude that both SecA1 and SecA2 individually form homodimers in solution but when both proteins are present simultaneously, they form dissociable heterodimers.
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Identification of small-molecule inhibitors against SecA by structure-based virtual ligand screening. J Antibiot (Tokyo) 2015; 68:666-73. [PMID: 25990955 DOI: 10.1038/ja.2015.53] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 03/17/2015] [Accepted: 04/13/2015] [Indexed: 12/28/2022]
Abstract
The rapid rise of antibiotic-resistant bacteria is one of the major concerns in modern medicine. Therefore, to treat bacterial infections, there is an urgent need for new antibacterials-preferably directed against alternative bacterial targets. One such potential target is the preprotein translocation motor SecA. SecA is a peripheral membrane ATPase and a key component of the Sec secretion pathway, the major route for bacterial protein export across or into the cytoplasmic membrane. As SecA is essential for bacterial viability, ubiquitous and highly conserved in bacteria, but not present in eukaryotic cells, it represents an attractive antibacterial target. Using an in silico approach, we have defined several potentially druggable and conserved pockets on the surface of SecA. We show that three of these potentially druggable sites are important for SecA function. A starting collection of ~500 000 commercially available small-molecules was virtually screened against a predicted druggable pocket in the preprotein-binding domain of Escherichia coli SecA using a multi-step virtual ligand screening protocol. The 1040 top-scoring molecules were tested in vitro for inhibition of the translocation ATPase activity of E. coli SecA. Five inhibitors of the translocation ATPase, and not of basal or membrane ATPase, were identified with IC50 values <65 μm. The most potent inhibitor showed an IC50 of 24 μm. The antimicrobial activity was determined for the five most potent SecA inhibitors. Two compounds were found to possess weak antibacterial activity (IC50 ~198 μm) against E. coli, whereas some compounds showed moderate antibacterial activity (IC50 ~100 μm) against Staphylococcus aureus.
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Rho JR, Subramaniam G, Choi H, Kim EH, Ng SP, Yoganathan K, Ng S, Buss AD, Butler MS, Gerwick WH. Gargantulide A, a complex 52-membered macrolactone showing antibacterial activity from Streptomyces sp. Org Lett 2015; 17:1377-80. [PMID: 25723256 DOI: 10.1021/acs.orglett.5b00068] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Gargantulide A (1), an extremely complex 52-membered macrolactone, was isolated from Streptomyces sp. A42983 and displayed moderate activity against MRSA. The planar structure of 1 was determined using 2D NMR, and its stereochemistry was partially established on the basis of NOESY correlations, J-based configuration analysis, and Kishi's universal NMR database.
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Affiliation(s)
- Jung-Rae Rho
- †Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, United States
| | - Gurusamy Subramaniam
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - Hyukjae Choi
- §Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States
| | - Eun-Hee Kim
- ∥Division of Magnetic Resonance, Korea Basic Science Institute, Ochang, Chungbuk 363-883, Korea
| | - Sok Peng Ng
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - K Yoganathan
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - Siewbee Ng
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - Antony D Buss
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - Mark S Butler
- ‡MerLion Pharmaceuticals, 41 Science Park Road, #04-03B the Gemini, Singapore Science Park II, Singapore 117610, Singapore
| | - William H Gerwick
- †Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, United States.,§Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States
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Dudek J, Pfeffer S, Lee PH, Jung M, Cavalié A, Helms V, Förster F, Zimmermann R. Protein transport into the human endoplasmic reticulum. J Mol Biol 2014; 427:1159-75. [PMID: 24968227 DOI: 10.1016/j.jmb.2014.06.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Accepted: 06/11/2014] [Indexed: 12/22/2022]
Abstract
Protein transport into the endoplasmic reticulum (ER) is essential for all eukaryotic cells and evolutionary related to protein transport into and across the cytoplasmic membrane of eubacteria and archaea. It is based on amino-terminal signal peptides in the precursor polypeptides plus various transport components in cytosol plus ER and can occur either cotranslationally or posttranslationally. The two mechanisms merge at the heterotrimeric Sec61 complex in the ER membrane, which forms an aqueous polypeptide-conducting channel. Since the mammalian ER is also the main intracellular calcium storage organelle, the Sec61 complex is tightly regulated in its dynamics between the open and closed conformations by various ligands, such as precursor polypeptides at the cytosolic face and the Hsp70-type molecular chaperone BiP at the ER lumenal face (Hsp, heat shock protein). Furthermore, BiP binding to the incoming precursor polypeptide contributes to unidirectionality and efficiency of transport. Recent insights into the structural dynamics of the Sec61 complex and related complexes in eubacteria and archaea have various mechanistic and functional implications.
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Affiliation(s)
- Johanna Dudek
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Po-Hsien Lee
- Computational Biology, Saarland University, 66041 Saarbrücken, Germany
| | - Martin Jung
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Volkhard Helms
- Computational Biology, Saarland University, 66041 Saarbrücken, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.
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45
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Wowor AJ, Yan Y, Auclair SM, Yu D, Zhang J, May ER, Gross ML, Kendall DA, Cole JL. Analysis of SecA dimerization in solution. Biochemistry 2014; 53:3248-60. [PMID: 24786965 PMCID: PMC4030788 DOI: 10.1021/bi500348p] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
![]()
The Sec pathway mediates translocation
of protein across the inner
membrane of bacteria. SecA is a motor protein that drives translocation
of preprotein through the SecYEG channel. SecA reversibly dimerizes
under physiological conditions, but different dimer interfaces have
been observed in SecA crystal structures. Here, we have used biophysical
approaches to address the nature of the SecA dimer that exists in
solution. We have taken advantage of the extreme salt sensitivity
of SecA dimerization to compare the rates of hydrogen–deuterium
exchange of the monomer and dimer and have analyzed the effects of
single-alanine substitutions on dimerization affinity. Our results
support the antiparallel dimer arrangement observed in one of the
crystal structures of Bacillus subtilis SecA. Additional
residues lying within the preprotein binding domain and the C-terminus
are also protected from exchange upon dimerization, indicating linkage
to a conformational transition of the preprotein binding domain from
an open to a closed state. In agreement with this interpretation,
normal mode analysis demonstrates that the SecA dimer interface influences
the global dynamics of SecA such that dimerization stabilizes the
closed conformation.
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Affiliation(s)
- Andy J Wowor
- Department of Pharmaceutical Sciences, University of Connecticut , Storrs, Connecticut 06269, United States
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