1
|
Levin R, Köck Z, Martin J, Zangl R, Gewering T, Schüler L, Moeller A, Dötsch V, Morgner N, Bernhard F. Cotranslational assembly of membrane protein/nanoparticles in cell-free systems. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184017. [PMID: 35921875 DOI: 10.1016/j.bbamem.2022.184017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 07/18/2022] [Accepted: 07/27/2022] [Indexed: 06/15/2023]
Abstract
Nanoparticles composed of amphiphilic scaffold proteins and small lipid bilayers are valuable tools for reconstitution and subsequent functional and structural characterization of membrane proteins. In combination with cell-free protein production systems, nanoparticles can be used to cotranslationally and translocon independently insert membrane proteins into tailored lipid environments. This strategy enables rapid generation of protein/nanoparticle complexes by avoiding detergent contact of nascent membrane proteins. Frequently in use are nanoparticles assembled with engineered derivatives of either the membrane scaffold protein (MSP) or the Saposin A (SapA) scaffold. Furthermore, several strategies for the formation of membrane protein/nanoparticle complexes in cell-free reactions exist. However, it is unknown how these strategies affect functional folding, oligomeric assembly and membrane insertion efficiency of cell-free synthesized membrane proteins. We systematically studied membrane protein insertion efficiency and sample quality of cell-free synthesized proteorhodopsin (PR) which was cotranslationally inserted in MSP and SapA based nanoparticles. Three possible PR/nanoparticle formation strategies were analyzed: (i) PR integration into supplied preassembled nanoparticles, (ii) coassembly of nanoparticles from supplied scaffold proteins and lipids upon PR expression, and (iii) coexpression of scaffold proteins together with PR in presence of supplied lipids. Yield, homogeneity as well as the formation of higher PR oligomeric complexes from samples generated by the three strategies were analyzed. Conditions found optimal for PR were applied for the synthesis of a G-protein coupled receptor. The study gives a comprehensive guideline for the rapid synthesis of membrane protein/nanoparticle samples by different processes and identifies key parameters to modulate sample yield and quality.
Collapse
Affiliation(s)
- Roman Levin
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany
| | - Zoe Köck
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany
| | - Janosch Martin
- Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany
| | - René Zangl
- Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany
| | | | - Leah Schüler
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany
| | - Arne Moeller
- University of Osnabrück, 49076 Osnabrück, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany
| | - Nina Morgner
- Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany
| | - Frank Bernhard
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany.
| |
Collapse
|
2
|
Korn V, Pluhackova K. Not sorcery after all: Roles of multiple charged residues in membrane insertion of gasdermin-A3. Front Cell Dev Biol 2022; 10:958957. [PMID: 36120563 PMCID: PMC9479151 DOI: 10.3389/fcell.2022.958957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/26/2022] [Indexed: 11/16/2022] Open
Abstract
Gasdermins execute programmatory cell death, known as pyroptosis, by forming medium-sized membrane pores. Recently, the molecular structure of those pores as well as the diversity in their shape and size have been revealed by cryoTEM and atomic force microscopy, respectively. Even though a growth of smaller to larger oligomers and reshaping from slits to rings could be documented, the initiation of the gasdermin pore formation remains a mystery. In one hypothesis, gasdermin monomers insert into membranes before associating into oligomeric pores. In the other hypothesis, gasdermin oligomers preassemble on the membrane surface prior to membrane insertion. Here, by studying the behavior of monomeric membrane-inserted gasdermin-A3 (GSDMA3), we unveil that a monomeric gasdermin prefers the membrane-adsorbed over the membrane-inserted state. Our results thus support the hypothesis of oligomers preassembling on the membrane surface before membrane penetration. At the same time, our simulations of small membrane-inserted arcs of GSDMA3 suggest that the inserting oligomer can be small and does not have to comprise a full ring of approximately 26-30 subunits. Moreover, our simulations have revealed an astonishingly large impact of salt-bridge formation and protein surroundings on the transmembrane passage of charged residues, reducing the energetic cost by up to 53% as compared to their free forms. The here observed free energy barrier of mere 5.6 kcal/mol for the membrane insertion of monomeric GSDMA3 explains the surprising ability of gasdermins to spontaneously self-insert into cellular membranes.
Collapse
Affiliation(s)
| | - Kristyna Pluhackova
- Stuttgart Center for Simulation Science, Cluster of Excellence EXC 2075, University of Stuttgart, Stuttgart, Germany
| |
Collapse
|
3
|
Wu Z, Zhang Y, Xu X, Ahmed T, Yang Y, Loh B, Leptihn S, Yan C, Chen J, Li B. The Holin-Endolysin Lysis System of the OP2-Like Phage X2 Infecting Xanthomonas oryzae pv. oryzae. Viruses 2021; 13:v13101949. [PMID: 34696380 PMCID: PMC8541568 DOI: 10.3390/v13101949] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/18/2021] [Accepted: 09/21/2021] [Indexed: 01/01/2023] Open
Abstract
Most endolysins of dsDNA phages are exported by a holin-dependent mechanism, while in some cases endolysins are exported via a holin-independent mechanism. However, it is still unclear whether the same endolysins can be exported by both holin-dependent and holin-independent mechanisms. This study investigated the lysis system of OP2-like phage X2 infecting Xanthomonas oryzae pv. oryzae, causing devastating bacterial leaf blight disease in rice. Based on bioinformatics and protein biochemistry methods, we show that phage X2 employs the classic "holin-endolysin" lysis system. The endolysin acts on the cell envelope and exhibits antibacterial effects in vitro, while the holin facilitates the release of the protein into the periplasm. We also characterized the role of the transmembrane domain (TMD) in the translocation of the endolysin across the inner membrane. We found that the TMD facilitated the translocation of the endolysin via the Sec secretion system. The holin increases the efficiency of protein release, leading to faster and more efficient lysis. Interestingly, in E. coli, the expression of either holin or endolysin with TMDs resulted in the formation of long rod shaped cells. We conclude that the TMD of X2-Lys plays a dual role: One is the transmembrane transport while the other is the inhibition of cell division, resulting in larger cells and thus in a higher number of released viruses per cell.
Collapse
Affiliation(s)
- Zhifeng Wu
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Z.W.); (Y.Z.); (X.X.); (T.A.)
| | - Yang Zhang
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Z.W.); (Y.Z.); (X.X.); (T.A.)
| | - Xinyang Xu
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Z.W.); (Y.Z.); (X.X.); (T.A.)
| | - Temoor Ahmed
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Z.W.); (Y.Z.); (X.X.); (T.A.)
| | - Yong Yang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; (Y.Y.); (C.Y.)
| | - Belinda Loh
- University of Edinburgh Institute, Zhejiang University, Hangzhou 314400, China; (B.L.); (S.L.)
| | - Sebastian Leptihn
- University of Edinburgh Institute, Zhejiang University, Hangzhou 314400, China; (B.L.); (S.L.)
| | - Chenqi Yan
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; (Y.Y.); (C.Y.)
- Institute of Plant Virology, Ningbo University, Ningbo 315211, China
| | - Jianping Chen
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; (Y.Y.); (C.Y.)
- Institute of Plant Virology, Ningbo University, Ningbo 315211, China
- Correspondence: (J.C.); (B.L.); Tel.: +86-571-8898-2412 (B.L.)
| | - Bin Li
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Z.W.); (Y.Z.); (X.X.); (T.A.)
- Correspondence: (J.C.); (B.L.); Tel.: +86-571-8898-2412 (B.L.)
| |
Collapse
|
4
|
Single-molecule fluorescence vistas of how lipids regulate membrane proteins. Biochem Soc Trans 2021; 49:1685-1694. [PMID: 34346484 DOI: 10.1042/bst20201074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 12/17/2022]
Abstract
The study of membrane proteins is undergoing a golden era, and we are gaining unprecedented knowledge on how this key group of proteins works. However, we still have only a basic understanding of how the chemical composition and the physical properties of lipid bilayers control the activity of membrane proteins. Single-molecule (SM) fluorescence methods can resolve sample heterogeneity, allowing to discriminate between the different molecular populations that biological systems often adopt. This short review highlights relevant examples of how SM fluorescence methodologies can illuminate the different ways in which lipids regulate the activity of membrane proteins. These studies are not limited to lipid molecules acting as ligands, but also consider how the physical properties of the bilayer can be determining factors on how membrane proteins function.
Collapse
|
5
|
Loh B, Gondil VS, Manohar P, Khan FM, Yang H, Leptihn S. Encapsulation and Delivery of Therapeutic Phages. Appl Environ Microbiol 2021; 87:AEM.01979-20. [PMID: 33310718 PMCID: PMC8090888 DOI: 10.1128/aem.01979-20] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Delivery of therapeutic compounds to the site of action is crucial. While many chemical substances such as beta-lactam antibiotics can reach therapeutic levels in most parts throughout the human body after administration, substances of higher molecular weight such as therapeutic proteins may not be able to reach the site of action (e.g. an infection), and are therefore ineffective. In the case of therapeutic phages, i.e. viruses that infect microbes that can be used to treat bacterial infections, this problem is exacerbated; not only are phages unable to penetrate tissues, but phage particles can be cleared by the immune system and phage proteins are rapidly degraded by enzymes or inactivated by the low pH in the stomach. Yet, the use of therapeutic phages is a highly promising strategy, in particular for infections caused by bacteria that exhibit multi-drug resistance. Clinicians increasingly encounter situations where no treatment options remain available for such infections, where antibiotic compounds are ineffective. While the number of drug-resistant pathogens continues to rise due to the overuse and misuse of antibiotics, no new compounds are becoming available as many pharmaceutical companies discontinue their search for chemical antimicrobials. In recent years, phage therapy has undergone massive innovation for the treatment of infections caused by pathogens resistant to conventional antibiotics. While most therapeutic applications of phages are well described in the literature, other aspects of phage therapy are less well documented. In this review, we focus on the issues that are critical for phage therapy to become a reliable standard therapy and describe methods for efficient and targeted delivery of phages, including their encapsulation.
Collapse
Affiliation(s)
- Belinda Loh
- Zhejiang University-University of Edinburgh (ZJU-UoE) Institute, Zhejiang University, International Campus, Haining, Zhejiang 314400, China and The Second Affiliated Hospital Zhejiang University (SAHZU), School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - Vijay Singh Gondil
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, P.R. China
| | - Prasanth Manohar
- Zhejiang University-University of Edinburgh (ZJU-UoE) Institute, Zhejiang University, International Campus, Haining, Zhejiang 314400, China and The Second Affiliated Hospital Zhejiang University (SAHZU), School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - Fazal Mehmood Khan
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, P.R. China
| | - Hang Yang
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, P.R. China
| | - Sebastian Leptihn
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, P.R. China.
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, PR China
- University of Edinburgh Medical School, Biomedical Sciences, College of Medicine & Veterinary Medicine, The University of Edinburgh, 1 George Square, Edinburgh, EH8 9JZ, United Kingdom
| |
Collapse
|
6
|
Nishikawa H, Kanno K, Endo Y, Nishiyama KI. Ring assembly of c subunits of F 0 F 1 -ATP synthase in Propionigenium modestum requires YidC and UncI following MPIase-dependent membrane insertion. FEBS Lett 2021; 595:647-654. [PMID: 33423295 DOI: 10.1002/1873-3468.14036] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/20/2020] [Accepted: 12/31/2020] [Indexed: 01/25/2023]
Abstract
The c subunits of F0 F1 -ATP synthase (F0 c) assemble into a ring structure, following membrane insertion that is dependent on both glycolipid MPIase and protein YidC. We analyzed the insertion and assembly processes of Propionigenium modestum F0 c (Pm-F0 c), of which the ring structure is resistant to SDS. Ring assembly of Pm-F0 c requires P. modestum UncI (Pm-UncI). Ring assembly of in vitro synthesized Pm-F0 c was observed when both YidC and Pm-UncI were reconstituted into liposomes of Escherichia coli phospholipids. Under the physiological conditions where spontaneous insertion had been blocked by diacylglycerol, MPIase was necessary for Pm-F0 c insertion allowing the subsequent YidC/Pm-UncI-dependent ring assembly. Thus, we have succeeded in the complete reconstitution of membrane insertion and subsequent ring assembly of Pm-F0 c.
Collapse
Affiliation(s)
- Hanako Nishikawa
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan
| | - Kotoka Kanno
- Department of Biological Chemistry and Food Science, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Yuta Endo
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan
| | - Ken-Ichi Nishiyama
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan.,Department of Biological Chemistry and Food Science, Faculty of Agriculture, Iwate University, Morioka, Japan
| |
Collapse
|
7
|
Shanmugam SK, Backes N, Chen Y, Belardo A, Phillips GJ, Dalbey RE. New Insights into Amino-Terminal Translocation as Revealed by the Use of YidC and Sec Depletion Strains. J Mol Biol 2019; 431:1025-1037. [DOI: 10.1016/j.jmb.2019.01.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 12/24/2018] [Accepted: 01/02/2019] [Indexed: 02/03/2023]
|
8
|
Iwamoto M, Elfaramawy MA, Yamatake M, Matsuura T, Oiki S. Concurrent In Vitro Synthesis and Functional Detection of Nascent Activity of the KcsA Channel under a Membrane Potential. ACS Synth Biol 2018; 7:1004-1011. [PMID: 29566487 DOI: 10.1021/acssynbio.7b00454] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Processes involved in the functional formation of prokaryotic membrane proteins have remained elusive. Here, we developed a new in vitro membrane protein expression system to detect nascent activities of the KcsA potassium channel in lipid bilayers under an applied membrane potential. The channel was synthesized using a reconstituted Escherichia coli-based in vitro transcription/translation system (IVTT) in a water-in-oil droplet lined by a membrane. The synthesized channels spontaneously incorporated into the membrane even without the translocon machinery (unassisted pathway) and formed functional channels with the correct orientation. The single-channel current of the first appearing nascent channel was captured, followed by the subsequent appearance of multiple channels. Notably, the first appearance time shortened substantially as the membrane potential was hyperpolarized. Under a steadily applied membrane potential, this system serves as a production line of membrane proteins via the unassisted pathway, mimicking the bacterial synthetic membrane.
Collapse
Affiliation(s)
- Masayuki Iwamoto
- Department of Molecular Physiology and Biophysics, University of Fukui, Eiheiji-cho, Fukui 910-1193, Japan
| | - Maie A. Elfaramawy
- Department of Biotechnology, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Mariko Yamatake
- Department of Molecular Physiology and Biophysics, University of Fukui, Eiheiji-cho, Fukui 910-1193, Japan
| | - Tomoaki Matsuura
- Department of Biotechnology, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics, University of Fukui, Eiheiji-cho, Fukui 910-1193, Japan
| |
Collapse
|
9
|
Renauld S, Cortes S, Bersch B, Henry X, De Waard M, Schaack B. Functional reconstitution of cell-free synthesized purified Kv channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2373-2380. [DOI: 10.1016/j.bbamem.2017.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/29/2017] [Accepted: 09/05/2017] [Indexed: 12/11/2022]
|
10
|
Kuhn A, Haase M, Leptihn S. Assisted and Unassisted Protein Insertion into Liposomes. Biophys J 2017; 113:1187-1193. [PMID: 28454841 PMCID: PMC5607036 DOI: 10.1016/j.bpj.2017.03.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/30/2017] [Accepted: 03/31/2017] [Indexed: 02/04/2023] Open
Abstract
The insertion of newly synthesized membrane proteins is a well-regulated and fascinating process occurring in every living cell. Several translocases and insertases have been found in prokaryotic and eukaryotic cells, the Sec61 complex and the Get complex in the endoplasmic reticulum and the SecYEG complex and YidC in bacteria and archaea. In mitochondria, TOM and TIM complexes transport nuclear-encoded proteins, whereas the Oxa1 is required for the insertion of mitochondria-encoded membrane proteins. Related to the bacterial YidC and the mitochondrial Oxa1 are the Alb3 and Alb4 proteins in chloroplasts. These membrane insertases are comparably simple and can be studied in vitro, after their biochemical purification and reconstitution in artificial lipid bilayers such as liposomes or nanodiscs. Here, we describe the recent progress to study the molecular mechanism of YidC-dependent and unassisted membrane insertion at the single molecule level.
Collapse
Affiliation(s)
- Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, Stuttgart, Germany
| | - Maximilian Haase
- Institute of Microbiology and Molecular Biology, University of Hohenheim, Stuttgart, Germany
| | - Sebastian Leptihn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, Stuttgart, Germany.
| |
Collapse
|
11
|
The Transmembrane Morphogenesis Protein gp1 of Filamentous Phages Contains Walker A and Walker B Motifs Essential for Phage Assembly. Viruses 2017; 9:v9040073. [PMID: 28397779 PMCID: PMC5408679 DOI: 10.3390/v9040073] [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: 02/08/2017] [Revised: 03/29/2017] [Accepted: 04/04/2017] [Indexed: 01/26/2023] Open
Abstract
In contrast to lytic phages, filamentous phages are assembled in the inner membrane and secreted across the bacterial envelope without killing the host. For assembly and extrusion of the phage across the host cell wall, filamentous phages code for membrane-embedded morphogenesis proteins. In the outer membrane of Escherichia coli, the protein gp4 forms a pore-like structure, while gp1 and gp11 form a complex in the inner membrane of the host. By comparing sequences with other filamentous phages, we identified putative Walker A and B motifs in gp1 with a conserved lysine in the Walker A motif (K14), and a glutamic and aspartic acid in the Walker B motif (D88, E89). In this work we demonstrate that both, Walker A and Walker B, are essential for phage production. The crucial role of these key residues suggests that gp1 might be a molecular motor driving phage assembly. We further identified essential residues for the function of the assembly complex. Mutations in three out of six cysteine residues abolish phage production. Similarly, two out of six conserved glycine residues are crucial for gp1 function. We hypothesise that the residues represent molecular hinges allowing domain movement for nucleotide binding and phage assembly.
Collapse
|
12
|
Abstract
The insertion and assembly of proteins into the inner membrane of bacteria are crucial for many cellular processes, including cellular respiration, signal transduction, and ion and pH homeostasis. This process requires efficient membrane targeting and insertion of proteins into the lipid bilayer in their correct orientation and proper conformation. Playing center stage in these events are the targeting components, signal recognition particle (SRP) and the SRP receptor FtsY, as well as the insertion components, the Sec translocon and the YidC insertase. Here, we will discuss new insights provided from the recent high-resolution structures of these proteins. In addition, we will review the mechanism by which a variety of proteins with different topologies are inserted into the inner membrane of Gram-negative bacteria. Finally, we report on the energetics of this process and provide information on how membrane insertion occurs in Gram-positive bacteria and Archaea. It should be noted that most of what we know about membrane protein assembly in bacteria is based on studies conducted in Escherichia coli.
Collapse
Affiliation(s)
- Andreas Kuhn
- Institute for Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Hans-Georg Koch
- Institute for Biochemistry and Molecular Biology, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany
| | - Ross E Dalbey
- Department of Chemistry, The Ohio State University, Columbus, OH 43210
| |
Collapse
|