1
|
Winkler K, Karner A, Horner A, Hannesschlaeger C, Knyazev D, Siligan C, Zimmermann M, Kuttner R, Pohl P, Preiner J. Interaction of the motor protein SecA and the bacterial protein translocation channel SecYEG in the absence of ATP. NANOSCALE ADVANCES 2020; 2:3431-3443. [PMID: 36134293 PMCID: PMC9418451 DOI: 10.1039/d0na00427h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/27/2020] [Indexed: 06/16/2023]
Abstract
Translocation of many secretory proteins through the bacterial plasma membrane is facilitated by a complex of the SecYEG channel with the motor protein SecA. The ATP-free complex is unstable in detergent, raising the question how SecA may perform several rounds of ATP hydrolysis without being released from the membrane embedded SecYEG. Here we show that dual recognition of (i) SecYEG and (ii) vicinal acidic lipids confers an apparent nanomolar affinity. High-speed atomic force microscopy visualizes the complexes between monomeric SecA and SecYEG as being stable for tens of seconds. These long-lasting events and complementary shorter ones both give rise to single ion channel openings of equal duration. Furthermore, luminescence resonance energy transfer reveals two conformations of the SecYEG-SecA complex that differ in the protrusion depth of SecA's two-helix finger into SecYEG's aqueous channel. Such movement of the finger is in line with the power stroke mechanism of protein translocation.
Collapse
Affiliation(s)
- Klemens Winkler
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Andreas Karner
- University of Applied Sciences Upper Austria, TIMED Center 4020 Linz Austria
| | - Andreas Horner
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | | | - Denis Knyazev
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Christine Siligan
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Mirjam Zimmermann
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Roland Kuttner
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Peter Pohl
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Johannes Preiner
- University of Applied Sciences Upper Austria, TIMED Center 4020 Linz Austria
| |
Collapse
|
2
|
Komarudin AG, Driessen AJM. SecA-Mediated Protein Translocation through the SecYEG Channel. Microbiol Spectr 2019; 7:10.1128/microbiolspec.psib-0028-2019. [PMID: 31373268 PMCID: PMC10957188 DOI: 10.1128/microbiolspec.psib-0028-2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Indexed: 01/02/2023] Open
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.
Collapse
Affiliation(s)
- Amalina Ghaisani Komarudin
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute of Advanced Materials, University of Groningen, Nijenborgh 7, 9747AG Groningen, The Netherlands
| | - Arnold J M Driessen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute of Advanced Materials, University of Groningen, Nijenborgh 7, 9747AG Groningen, The Netherlands
| |
Collapse
|
3
|
Jin J, Hsieh YH, Chaudhary AS, Cui J, Houghton JE, Sui SF, Wang B, Tai PC. SecA inhibitors as potential antimicrobial agents: differential actions on SecA-only and SecA-SecYEG protein-conducting channels. FEMS Microbiol Lett 2018; 365:5037921. [PMID: 30007321 PMCID: PMC7190897 DOI: 10.1093/femsle/fny145] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 06/13/2018] [Indexed: 12/13/2022] Open
Abstract
Sec-dependent protein translocation is an essential process in bacteria. SecA is a key component of the translocation machinery and has multiple domains that interact with various ligands. SecA acts as an ATPase motor to drive the precursor protein/peptide through the SecYEG protein translocation channels. As SecA is unique to bacteria and there is no mammalian counterpart, it is an ideal target for the development of new antimicrobials. Several reviews detail the assays for ATPase and protein translocation, as well as the search for SecA inhibitors. Recent studies have shown that, in addition to the SecA-SecYEG translocation channels, there are SecA-only channels in the lipid bilayers, which function independently from the SecYEG machinery. This mini-review focuses on recent advances on the newly developed SecA inhibitors that allow the evaluation of their potential as antimicrobial agents, as well as a fundamental understanding of mechanisms of SecA function(s). These SecA inhibitors abrogate the effects of efflux pumps in both Gram-positive and Gram-negative bacteria. We also discuss recent findings that SecA binds to ribosomes and nascent peptides, which suggest other roles of SecA. A model for the multiple roles of SecA is presented.
Collapse
Affiliation(s)
- Jinshan Jin
- Department of Biology, Center for Biotechnology and Drug Design and Georgia State University, Atlanta, GA 30303, USA
| | - Ying-Hsin Hsieh
- Department of Biology, Center for Biotechnology and Drug Design and Georgia State University, Atlanta, GA 30303, USA
| | - Arpana S Chaudhary
- Department of Chemistry, Center for Biotechnology and Drug Design and Georgia State University, P.O. Box 3965, Atlanta, GA 30303, USA
| | - Jianmei Cui
- Department of Chemistry, Center for Biotechnology and Drug Design and Georgia State University, P.O. Box 3965, Atlanta, GA 30303, USA
| | - John E Houghton
- Department of Biology, Center for Biotechnology and Drug Design and Georgia State University, Atlanta, GA 30303, USA
| | - Sen-fang Sui
- State Key Laboratory of Membrane Biology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Binghe Wang
- Department of Chemistry, Center for Biotechnology and Drug Design and Georgia State University, P.O. Box 3965, Atlanta, GA 30303, USA
| | - Phang C Tai
- Department of Biology, Center for Biotechnology and Drug Design and Georgia State University, Atlanta, GA 30303, USA
| |
Collapse
|
4
|
Specific cardiolipin-SecY interactions are required for proton-motive force stimulation of protein secretion. Proc Natl Acad Sci U S A 2018; 115:7967-7972. [PMID: 30012626 DOI: 10.1073/pnas.1721536115] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The transport of proteins across or into membranes is a vital biological process, achieved in every cell by the conserved Sec machinery. In bacteria, SecYEG combines with the SecA motor protein for secretion of preproteins across the plasma membrane, powered by ATP hydrolysis and the transmembrane proton-motive force (PMF). The activities of SecYEG and SecA are modulated by membrane lipids, particularly cardiolipin (CL), a specialized phospholipid known to associate with a range of energy-transducing machines. Here, we identify two specific CL binding sites on the Thermotoga maritima SecA-SecYEG complex, through application of coarse-grained molecular dynamics simulations. We validate the computational data and demonstrate the conserved nature of the binding sites using in vitro mutagenesis, native mass spectrometry, biochemical analysis, and fluorescence spectroscopy of Escherichia coli SecYEG. The results show that the two sites account for the preponderance of functional CL binding to SecYEG, and mediate its roles in ATPase and protein transport activity. In addition, we demonstrate an important role for CL in the conferral of PMF stimulation of protein transport. The apparent transient nature of the CL interaction might facilitate proton exchange with the Sec machinery, and thereby stimulate protein transport, by a hitherto unexplored mechanism. This study demonstrates the power of coupling the high predictive ability of coarse-grained simulation with experimental analyses, toward investigation of both the nature and functional implications of protein-lipid interactions.
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
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.
Collapse
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.
| |
Collapse
|
7
|
Hsieh YH, Huang YJ, Zhang H, Liu Q, Lu Y, Yang H, Houghton J, Jiang C, Sui SF, Tai PC. Dissecting structures and functions of SecA-only protein-conducting channels: ATPase, pore structure, ion channel activity, protein translocation, and interaction with SecYEG/SecDF•YajC. PLoS One 2017; 12:e0178307. [PMID: 28575061 PMCID: PMC5456053 DOI: 10.1371/journal.pone.0178307] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/10/2017] [Indexed: 11/30/2022] Open
Abstract
SecA is an essential protein in the major bacterial Sec-dependent translocation pathways. E. coli SecA has 901 aminoacyl residues which form multi-functional domains that interact with various ligands to impart function. In this study, we constructed and purified tethered C-terminal deletion fragments of SecA to determine the requirements for N-terminal domains interacting with lipids to provide ATPase activity, pore structure, ion channel activity, protein translocation and interactions with SecYEG-SecDF•YajC. We found that the N-terminal fragment SecAN493 (SecA1-493) has low, intrinsic ATPase activity. Larger fragments have greater activity, becoming highest around N619-N632. Lipids greatly stimulated the ATPase activities of the fragments N608-N798, reaching maximal activities around N619. Three helices in amino-acyl residues SecA619-831, which includes the "Helical Scaffold" Domain (SecA619-668) are critical for pore formation, ion channel activity, and for function with SecYEG-SecDF•YajC. In the presence of liposomes, N-terminal domain fragments of SecA form pore-ring structures at fragment-size N640, ion channel activity around N798, and protein translocation capability around N831. SecA domain fragments ranging in size between N643-N669 are critical for functional interactions with SecYEG-SecDF•YajC. In the presence of liposomes, inactive C-terminal fragments complement smaller non-functional N-terminal fragments to form SecA-only pore structures with ion channel activity and protein translocation ability. Thus, SecA domain fragment interactions with liposomes defined critical structures and functional aspects of SecA-only channels. These data provide the mechanistic basis for SecA to form primitive, low-efficiency, SecA-only protein-conducting channels, as well as the minimal parameters for SecA to interact functionally with SecYEG-SecDF•YajC to form high-efficiency channels.
Collapse
Affiliation(s)
- Ying-hsin Hsieh
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Ying-ju Huang
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Hao Zhang
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Qian Liu
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Yang Lu
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Hsiuchin Yang
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - John Houghton
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Chun Jiang
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| | - Sen-Fang Sui
- State Key Laboratory of Membrane Biology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing China
| | - Phang C. Tai
- Department of Biology, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, United States of America
| |
Collapse
|
8
|
Jin J, Hsieh YH, Cui J, Damera K, Dai C, Chaudhary AS, Zhang H, Yang H, Cao N, Jiang C, Vaara M, Wang B, Tai PC. Using Chemical Probes to Assess the Feasibility of Targeting SecA for Developing Antimicrobial Agents against Gram-Negative Bacteria. ChemMedChem 2016; 11:2511-2521. [PMID: 27753464 PMCID: PMC5189635 DOI: 10.1002/cmdc.201600421] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 09/25/2016] [Indexed: 11/07/2022]
Abstract
With the widespread emergence of drug resistance, there is an urgent need to search for new antimicrobials, especially those against Gram-negative bacteria. Along this line, the identification of viable targets is a critical first step. The protein translocase SecA is commonly believed to be an excellent target for the development of broad-spectrum antimicrobials. In recent years, we developed three structural classes of SecA inhibitors that have proven to be very effective against Gram-positive bacteria. However, we have not achieved the same level of success against Gram-negative bacteria, despite the potent inhibition of SecA in enzyme assays by the same inhibitors. In this study, we use representative inhibitors as chemical probes to gain an understanding as to why these inhibitors were not effective against Gram-negative bacteria. The results validate our initial postulation that the major difference in effectiveness against Gram-positive and Gram-negative bacteria is in the additional permeability barrier posed by the outer membrane of Gram-negative bacteria. We also found that the expression of efflux pumps, which are responsible for multidrug resistance (MDR), have no effect on the effectiveness of these SecA inhibitors. Identification of an inhibitor-resistant mutant and complementation tests of the plasmids containing secA in a secAts mutant showed that a single secA-azi-9 mutation increased the resistance, providing genetic evidence that SecA is indeed the target of these inhibitors in bacteria. Such results strongly suggest SecA as an excellent target for developing effective antimicrobials against Gram-negative bacteria with the intrinsic ability to overcome MDR. A key future research direction should be the optimization of membrane permeability.
Collapse
Affiliation(s)
- Jinshan Jin
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Ying-Hsin Hsieh
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Jianmei Cui
- Department of Chemistry, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Krishna Damera
- Department of Chemistry, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Chaofeng Dai
- Department of Chemistry, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Arpana S. Chaudhary
- Department of Chemistry, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Hao Zhang
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Hsiuchin Yang
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Nannan Cao
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Chun Jiang
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Martti Vaara
- Division of Clinical Microbiology, Helsinki University Hospital, FI-00029 HUSLAB, Helsinki, Finland, and Northern Antibiotics Ltd, FI-00720, Helsinki, Finland
| | - Binghe Wang
- Department of Chemistry, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| | - Phang C. Tai
- Department of Biology, Center for Biotechnology and Drug Design, and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303
| |
Collapse
|
9
|
Koch S, de Wit JG, Vos I, Birkner JP, Gordiichuk P, Herrmann A, van Oijen AM, Driessen AJM. Lipids Activate SecA for High Affinity Binding to the SecYEG Complex. J Biol Chem 2016; 291:22534-22543. [PMID: 27613865 DOI: 10.1074/jbc.m116.743831] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 08/30/2016] [Indexed: 11/06/2022] Open
Abstract
Protein translocation across the bacterial cytoplasmic membrane is an essential process catalyzed predominantly by the Sec translocase. This system consists of the membrane-embedded protein-conducting channel SecYEG, the motor ATPase SecA, and the heterotrimeric SecDFyajC membrane protein complex. Previous studies suggest that anionic lipids are essential for SecA activity and that the N terminus of SecA is capable of penetrating the lipid bilayer. The role of lipid binding, however, has remained elusive. By employing differently sized nanodiscs reconstituted with single SecYEG complexes and comprising varying amounts of lipids, we establish that SecA gains access to the SecYEG complex via a lipid-bound intermediate state, whereas acidic phospholipids allosterically activate SecA for ATP-dependent protein translocation.
Collapse
Affiliation(s)
- Sabrina Koch
- From the Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials and
| | - Janny G de Wit
- From the Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials and
| | - Iuliia Vos
- From the Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials and
| | - Jan Peter Birkner
- the Single-molecule Biophysics, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Pavlo Gordiichuk
- the Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, 9747 AG, Groningen, The Netherlands, and
| | - Andreas Herrmann
- the Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, 9747 AG, Groningen, The Netherlands, and
| | - Antoine M van Oijen
- the Single-molecule Biophysics, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands.,the School of Chemistry, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Arnold J M Driessen
- From the Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials and
| |
Collapse
|
10
|
Keller RCA. The role and significance of potential lipid-binding regions in the mitochondrial protein import motor: an in-depth in silico study. 3 Biotech 2015; 5:1041-1051. [PMID: 28324412 PMCID: PMC4624131 DOI: 10.1007/s13205-015-0310-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 05/12/2015] [Indexed: 12/05/2022] Open
Abstract
Over the last two decades, an impressive progress has been made in the identification of novel factors in the translocation machineries of the mitochondrial protein import and their possible roles. The role of lipids and possible protein–lipids interactions remains a relatively unexplored territory. Investigating the role of potential lipid-binding regions in the sub-units of the mitochondrial motor might help to shed some more light in our understanding of protein–lipid interactions mechanistically. Bioinformatics results seem to indicate multiple potential lipid-binding regions in each of the sub-units. The subsequent characterization of some of those regions in silico provides insight into the mechanistic functioning of this intriguing and essential part of the protein translocation machinery. Details about the way the regions interact with phospholipids were found by the use of Monte Carlo simulations. For example, Pam18 contains one possible transmembrane region and two tilted surface bound conformations upon interaction with phospholipids. The results demonstrate that the presented bioinformatics approach might be useful in an attempt to expand the knowledge of the possible role of protein–lipid interactions in the mitochondrial protein translocation process.
Collapse
Affiliation(s)
- Rob C A Keller
- Section Chemistry, Charlemagne College, Wilhelminastraat 13-15, 6524 AJ, Nijmegen, The Netherlands.
| |
Collapse
|
11
|
Na B, You Z, Yang H, Tai PC. Characterization of the minimal length of functional SecA in Escherichia coli. Biochem Biophys Res Commun 2014; 456:213-8. [PMID: 25446126 DOI: 10.1016/j.bbrc.2014.11.061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 11/14/2014] [Indexed: 12/01/2022]
Abstract
Previous studies showed that certain regions of E. coli SecA can be deleted from its N- and/or C-termini to complement a SecA amber ts mutant. In this study, we determined and characterized the dispensability of both ends of SecA molecules. With N-terminal intact or 9-aa deleted, 826aa (SecA1-826 and SecA10-826, respectively) is the minimum for complementation activity, while with N-terminus deleted by 2-21aa, SecA22-829 is the minimum. Further deletion at the C-terminus of SecA1-826/SecA10-826/SecA22-829 abolished the complementation activity in the cells. A hydrophobic amino acid is required for the 826th residue in the minimal-length SecAs. Chemical crosslinking and gel filtration result showed that both purified SecA22-828 and SecA22-829 could form a dimer. Moreover, the in vitro ATPase and protein translocation activities of SecA22-828 and SecA22-829 were similar, though lower than wild-type SecA. The active mutants had more truncated SecA in soluble than membrane-bound form, but was more stably embedded in membranes. In contrast, the inactive mutants tended to have truncated SecA more membrane-bound than soluble form, and were more loosely bound and easily chased out. Thus, the loss of complementation appears to be related to their altered subcellular localization and stability in the membranes. This study defines the substantial regions of N- and C-termini of SecA that may be deleted without losing complementation activity.
Collapse
Affiliation(s)
- Bing Na
- Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States
| | - Zhipeng You
- Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States
| | - Hsiuchin Yang
- Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States
| | - Phang C Tai
- Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States.
| |
Collapse
|