1
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Schoenmakers LLJ, den Uijl MJ, Postma JL, van den Akker TAP, Huck WTS, Driessen AJM. SecYEG-mediated translocation in a model synthetic cell. Synth Biol (Oxf) 2024; 9:ysae007. [PMID: 38807757 PMCID: PMC11131593 DOI: 10.1093/synbio/ysae007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 04/19/2024] [Accepted: 05/07/2024] [Indexed: 05/30/2024] Open
Abstract
Giant unilamellar vesicles (GUVs) provide a powerful model compartment for synthetic cells. However, a key challenge is the incorporation of membrane proteins that allow for transport, energy transduction, compartment growth and division. Here, we have successfully incorporated the membrane protein complex SecYEG-the key bacterial translocase that is essential for the incorporation of newly synthesized membrane proteins-in GUVs. Our method consists of fusion of small unilamellar vesicles containing reconstituted SecYEG into GUVs, thereby forming SecGUVs. These are suitable for large-scale experiments while maintaining a high protein:lipid ratio. We demonstrate that incorporation of SecYEG into GUVs does not inhibit its translocation efficiency. Robust membrane protein functionalized proteo-GUVs are promising and flexible compartments for use in the formation and growth of synthetic cells.
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Affiliation(s)
- Ludo L J Schoenmakers
- Physical-Organic Chemistry, Institute for Molecules and Materials, Radboud University, Nijmegen 6525AJ, The Netherlands
| | - Max J den Uijl
- Groningen Biomolecular Sciences and Biotechnology, Molecular Biotechnology, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Jelle L Postma
- General Instrumentation, Radboud University, Nijmegen 6525 AJ, The Netherlands
| | - Tim A P van den Akker
- Groningen Biomolecular Sciences and Biotechnology, Molecular Biotechnology, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Wilhelm T S Huck
- Physical-Organic Chemistry, Institute for Molecules and Materials, Radboud University, Nijmegen 6525AJ, The Netherlands
| | - Arnold J M Driessen
- Groningen Biomolecular Sciences and Biotechnology, Molecular Biotechnology, University of Groningen, Groningen 9747 AG, The Netherlands
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2
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den Uijl MJ, Driessen AJM. Phospholipid dependency of membrane protein insertion by the Sec translocon. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184232. [PMID: 37734458 DOI: 10.1016/j.bbamem.2023.184232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 09/08/2023] [Accepted: 09/14/2023] [Indexed: 09/23/2023]
Abstract
Membrane protein insertion into and translocation across the bacterial cytoplasmic membrane are essential processes facilitated by the Sec translocon. Membrane insertion occurs co-translationally whereby the ribosome nascent chain is targeted to the translocon via signal recognition particle and its receptor FtsY. The phospholipid dependence of membrane protein insertion has remained mostly unknown. Here we assessed in vitro the dependence of the SecA independent insertion of the mannitol permease MtlA into the membrane on the main phospholipid species present in Escherichia coli. We observed that insertion depends on the presence of phosphatidylglycerol and is due to the anionic nature of the polar headgroup, while insertion is stimulated by the zwitterionic phosphatidylethanolamine. We found an optimal insertion efficiency at about 30 mol% DOPG and 50 mol% DOPE which approaches the bulk membrane phospholipid composition of E. coli.
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Affiliation(s)
- Max J den Uijl
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology, 9747 AG Groningen, the Netherlands
| | - Arnold J M Driessen
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology, 9747 AG Groningen, the Netherlands.
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3
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Zerbetto De Palma G, Recoulat Angelini AA, Vitali V, González Flecha FL, Alleva K. Cooperativity in regulation of membrane protein function: phenomenological analysis of the effects of pH and phospholipids. Biophys Rev 2023; 15:721-731. [PMID: 37681089 PMCID: PMC10480370 DOI: 10.1007/s12551-023-01095-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 07/01/2023] [Indexed: 09/09/2023] Open
Abstract
Interaction between membrane proteins and ligands plays a key role in governing a wide spectrum of cellular processes. These interactions can provide a cooperative-type regulation of protein function. A wide variety of proteins, including enzymes, channels, transporters, and receptors, displays cooperative behavior in their interactions with ligands. Moreover, the ligands involved encompass a vast diversity and include specific molecules or ions that bind to specific binding sites. In this review, our particular focus is on the interaction between integral membrane proteins and ligands that can present multiple "binding sites", such as protons or membrane phospholipids. The study of the interaction that protons or lipids have with membrane proteins often presents challenges for classical mechanistic modeling approaches. In this regard, we show that, like Hill's pioneering work on hemoglobin regulation, phenomenological modeling constitutes a powerful tool for capturing essential features of these systems.
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Affiliation(s)
- Gerardo Zerbetto De Palma
- Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Biotecnología, Universidad Nacional de Hurlingham, Villa Tesei, Buenos Aires, Argentina
- Instituto de Química y Fisicoquímica Biológica (IQUIFIB), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Alvaro A. Recoulat Angelini
- Instituto de Química y Fisicoquímica Biológica (IQUIFIB), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Victoria Vitali
- Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Química y Fisicoquímica Biológica (IQUIFIB), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - F. Luis. González Flecha
- Instituto de Química y Fisicoquímica Biológica (IQUIFIB), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Karina Alleva
- Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Química y Fisicoquímica Biológica (IQUIFIB), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina
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4
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Moon S, Ham S, Jeong J, Ku H, Kim H, Lee C. Temperature Matters: Bacterial Response to Temperature Change. J Microbiol 2023; 61:343-357. [PMID: 37010795 DOI: 10.1007/s12275-023-00031-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/13/2023] [Accepted: 02/13/2023] [Indexed: 04/04/2023]
Abstract
Temperature is one of the most important factors in all living organisms for survival. Being a unicellular organism, bacterium requires sensitive sensing and defense mechanisms to tolerate changes in temperature. During a temperature shift, the structure and composition of various cellular molecules including nucleic acids, proteins, and membranes are affected. In addition, numerous genes are induced during heat or cold shocks to overcome the cellular stresses, which are known as heat- and cold-shock proteins. In this review, we describe the cellular phenomena that occur with temperature change and bacterial responses from a molecular perspective, mainly in Escherichia coli.
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Affiliation(s)
- Seongjoon Moon
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea
| | - Soojeong Ham
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea
| | - Juwon Jeong
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea
| | - Heechan Ku
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea
| | - Hyunhee Kim
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea.
| | - Changhan Lee
- Department of Biological Sciences, Ajou University, Suwon, 16499, Republic of Korea.
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5
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Role of a bacterial glycolipid in Sec-independent membrane protein insertion. Sci Rep 2022; 12:12231. [PMID: 35851412 PMCID: PMC9293918 DOI: 10.1038/s41598-022-16304-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 07/07/2022] [Indexed: 11/08/2022] Open
Abstract
Non-proteinaceous components in membranes regulate membrane protein insertion cooperatively with proteinaceous translocons. An endogenous glycolipid in the Escherichia coli membrane called membrane protein integrase (MPIase) is one such component. Here, we focused on the Sec translocon-independent pathway and examined the mechanisms of MPIase-facilitated protein insertion using physicochemical techniques. We determined the membrane insertion efficiency of a small hydrophobic protein using solid-state nuclear magnetic resonance, which showed good agreement with that determined by the insertion assay using an in vitro translation system. The observed insertion efficiency was strongly correlated with membrane physicochemical properties measured using fluorescence techniques. Diacylglycerol, a trace component of E. coli membrane, reduced the acyl chain mobility in the core region and inhibited the insertion, whereas MPIase restored them. We observed the electrostatic intermolecular interactions between MPIase and the side chain of basic amino acids in the protein, suggesting that the negatively charged pyrophosphate of MPIase attracts the positively charged residues of a protein near the membrane surface, which triggers the insertion. Thus, this study demonstrated the ingenious approach of MPIase to support membrane insertion of proteins by using its unique molecular structure in various ways.
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6
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Kamel M, Löwe M, Schott-Verdugo S, Gohlke H, Kedrov A. Unsaturated fatty acids augment protein transport via the SecA:SecYEG translocon. FEBS J 2021; 289:140-162. [PMID: 34312977 DOI: 10.1111/febs.16140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/01/2021] [Accepted: 07/23/2021] [Indexed: 12/22/2022]
Abstract
The translocon SecYEG and the associated ATPase SecA form the primary protein secretion system in the cytoplasmic membrane of bacteria. The secretion is essentially dependent on the surrounding lipids, but the mechanistic understanding of their role in SecA : SecYEG activity is sparse. Here, we reveal that the unsaturated fatty acids (UFAs) of the membrane phospholipids, including tetraoleoyl-cardiolipin, stimulate SecA : SecYEG-mediated protein translocation up to ten-fold. Biophysical analysis and molecular dynamics simulations show that UFAs increase the area per lipid and cause loose packing of lipid head groups, where the N-terminal amphipathic helix of SecA docks. While UFAs do not affect the translocon folding, they promote SecA binding to the membrane, and the effect is enhanced up to fivefold at elevated ionic strength. Tight SecA : lipid interactions convert into the augmented translocation. Our results identify the fatty acid structure as a notable factor in SecA : SecYEG activity, which may be crucial for protein secretion in bacteria, which actively change their membrane composition in response to their habitat.
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Affiliation(s)
- Michael Kamel
- Synthetic Membrane Systems, Institute for Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Maryna Löwe
- Synthetic Membrane Systems, Institute for Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Stephan Schott-Verdugo
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Germany.,John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Bioinformatics), and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Germany.,John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Bioinformatics), and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Germany
| | - Alexej Kedrov
- Synthetic Membrane Systems, Institute for Biochemistry, Heinrich Heine University Düsseldorf, Germany
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7
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Koch S, Seinen AB, Kamel M, Kuckla D, Monzel C, Kedrov A, Driessen AJM. Single-molecule analysis of dynamics and interactions of the SecYEG translocon. FEBS J 2020; 288:2203-2221. [PMID: 33058437 DOI: 10.1111/febs.15596] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 09/11/2020] [Accepted: 10/12/2020] [Indexed: 12/19/2022]
Abstract
Protein translocation and insertion into the bacterial cytoplasmic membrane are the essential processes mediated by the Sec machinery. The core machinery is composed of the membrane-embedded translocon SecYEG that interacts with the secretion-dedicated ATPase SecA and translating ribosomes. Despite the simplicity and the available structural insights on the system, diverse molecular mechanisms and functional dynamics have been proposed. Here, we employ total internal reflection fluorescence microscopy to study the oligomeric state and diffusion of SecYEG translocons in supported lipid bilayers at the single-molecule level. Silane-based coating ensured the mobility of lipids and reconstituted translocons within the bilayer. Brightness analysis suggested that approx. 70% of the translocons were monomeric. The translocons remained in a monomeric form upon ribosome binding, but partial oligomerization occurred in the presence of nucleotide-free SecA. Individual trajectories of SecYEG in the lipid bilayer revealed dynamic heterogeneity of diffusion, as translocons commonly switched between slow and fast mobility modes with corresponding diffusion coefficients of 0.03 and 0.7 µm2 ·s-1 . Interactions with SecA ATPase had a minor effect on the lateral mobility, while bound ribosome:nascent chain complexes substantially hindered the diffusion of single translocons. Notably, the mobility of the translocon:ribosome complexes was not affected by the solvent viscosity or macromolecular crowding modulated by Ficoll PM 70, so it was largely determined by interactions within the lipid bilayer and at the interface. We suggest that the complex mobility of SecYEG arises from the conformational dynamics of the translocon and protein:lipid interactions.
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Affiliation(s)
- Sabrina Koch
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands
| | - Anne-Bart Seinen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands.,Biophysics, AMOLF, Amsterdam, The Netherlands
| | - Michael Kamel
- Synthetic Membrane Systems, Institute of Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Daniel Kuckla
- Experimental Medical Physics, Department of Physics, Heinrich Heine University Düsseldorf, Germany
| | - Cornelia Monzel
- Experimental Medical Physics, Department of Physics, Heinrich Heine University Düsseldorf, Germany
| | - Alexej Kedrov
- Synthetic Membrane Systems, Institute of Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Arnold J M Driessen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands
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8
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Corin K, Bowie JU. How bilayer properties influence membrane protein folding. Protein Sci 2020; 29:2348-2362. [PMID: 33058341 DOI: 10.1002/pro.3973] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/07/2020] [Accepted: 10/09/2020] [Indexed: 01/24/2023]
Abstract
The question of how proteins manage to organize into a unique three-dimensional structure has been a major field of study since the first protein structures were determined. For membrane proteins, the question is made more complex because, unlike water-soluble proteins, the solvent is not homogenous or even unique. Each cell and organelle has a distinct lipid composition that can change in response to environmental stimuli. Thus, the study of membrane protein folding requires not only understanding how the unfolded chain navigates its way to the folded state, but also how changes in bilayer properties can affect that search. Here we review what we know so far about the impact of lipid composition on bilayer physical properties and how those properties can affect folding. A better understanding of the lipid bilayer and its effects on membrane protein folding is not only important for a theoretical understanding of the folding process, but can also have a practical impact on our ability to work with and design membrane proteins.
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Affiliation(s)
- Karolina Corin
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
| | - James U Bowie
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
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9
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Saha S. Association between the membrane transporter proteins and type 2 diabetes mellitus. Expert Rev Clin Pharmacol 2020; 13:287-297. [PMID: 32066279 DOI: 10.1080/17512433.2020.1729125] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Introduction: The prevalence rate of diabetes is increasing day by day and the current scenario of the available agents for its treatment has given rise to stimulation in the search for new therapeutic targets and agents. Therefore the present review will examine the role of membrane composition in the pathophysiology of Type 2 Diabetes and the possible therapeutic approaches for this.Areas covered: Glucose transporter proteins (GLUTs) are integral membrane proteins which are responsible for facilitated glucose transport over the plasma membrane into cells. Thus, this chapter is an attempt to interpret the co-relation between membrane transporter proteins and lipid molecules of cell membrane and their implications in type 2 diabetes mellitus. The relationship between the composition controlled flexibility of the membrane in the insertion of GLUTs into cell membrane as well as its fusion with the membrane is the focus of this chapter.Expert opinion: There is increasing data on the central role of phospholipid composition toward T2DM. Plasma membrane lipid composition plays a key role in maintaining the machinery for insulin-independent GLUT insertion into the membrane as well as insulin-dependent GLUT4 containing vesicles. As a therapeutic option, the designing of new chemical entities should be aimed to decrease saturated fatty acids of lipid bilayer phospholipids to target type 2 diabetes mellitus.
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Affiliation(s)
- Sarmistha Saha
- Department of Zoology, University School of Sciences, Gujarat University, Ahmedabad, India
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10
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Abstract
To identify the translocation components in cells, and to understand how they function in protein transport and membrane insertion, a variety of techniques have been used such as genetics, biochemistry, structural biology and single molecule methods. In particular, site-directed crosslinking between the client proteins and components of the translocation machineries have contributed significantly in the past and will do so in the future. One advantage of this technology is that it can be applied in vivo as well as in vitro and a comparison of the two approaches can be made. Also, the in vivo techniques allow time-dependent protocols which are essential for studying cellular pathways. Protein purification and reconstitution into proteoliposomes are the gold standard for studying membrane-based transport and translocation systems. With these biochemically defined approaches the function of each component in protein transport can be addressed individually with a plethora of biophysical techniques. Recently, the use of nanodiscs for reconstitution has added another extension of this reductionistic approach. Fluorescence based studies, cryo-microscopy and NMR spectroscopy have significantly added to our understanding how proteins move into and across membranes and will do this also in future.
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Affiliation(s)
- Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599, Stuttgart, Germany.
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11
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Kater L, Frieg B, Berninghausen O, Gohlke H, Beckmann R, Kedrov A. Partially inserted nascent chain unzips the lateral gate of the Sec translocon. EMBO Rep 2019; 20:e48191. [PMID: 31379073 PMCID: PMC6776908 DOI: 10.15252/embr.201948191] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/10/2019] [Accepted: 07/16/2019] [Indexed: 12/25/2022] Open
Abstract
The Sec translocon provides the lipid bilayer entry for ribosome-bound nascent chains and thus facilitates membrane protein biogenesis. Despite the appreciated role of the native environment in the translocon:ribosome assembly, structural information on the complex in the lipid membrane is scarce. Here, we present a cryo-electron microscopy-based structure of bacterial translocon SecYEG in lipid nanodiscs and elucidate an early intermediate state upon insertion of the FtsQ anchor domain. Insertion of the short nascent chain causes initial displacements within the lateral gate of the translocon, where α-helices 2b, 7, and 8 tilt within the membrane core to "unzip" the gate at the cytoplasmic side. Molecular dynamics simulations demonstrate that the conformational change is reversed in the absence of the ribosome, and suggest that the accessory α-helices of SecE subunit modulate the lateral gate conformation. Site-specific cross-linking validates that the FtsQ nascent chain passes the lateral gate upon insertion. The structure and the biochemical data suggest that the partially inserted nascent chain remains highly flexible until it acquires the transmembrane topology.
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Affiliation(s)
- Lukas Kater
- Gene Center MunichLudwig‐Maximilian‐UniversityMunichGermany
| | - Benedikt Frieg
- John von Neumann Institute for ComputingJülich Supercomputing CentreInstitute for Complex Systems ‐ Structural Biochemistry (ICS‐6)Forschungszentrum Jülich GmbHJülichGermany
| | | | - Holger Gohlke
- John von Neumann Institute for ComputingJülich Supercomputing CentreInstitute for Complex Systems ‐ Structural Biochemistry (ICS‐6)Forschungszentrum Jülich GmbHJülichGermany
- Institute for Pharmaceutical and Medicinal ChemistryHeinrich Heine University DüsseldorfDüsseldorfGermany
| | | | - Alexej Kedrov
- Gene Center MunichLudwig‐Maximilian‐UniversityMunichGermany
- Synthetic Membrane SystemsInstitute for BiochemistryHeinrich Heine University DüsseldorfDüsseldorfGermany
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12
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Koch S, Exterkate M, López CA, Patro M, Marrink SJ, Driessen AJM. Two distinct anionic phospholipid-dependent events involved in SecA-mediated protein translocation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183035. [PMID: 31394098 DOI: 10.1016/j.bbamem.2019.183035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 12/15/2022]
Abstract
Protein translocation across the bacterial cytoplasmic membrane is an essential process catalyzed by the Sec translocase, which in its minimal form consists of the protein-conducting channel SecYEG, and the motor ATPase SecA. SecA binds via its positively charged N-terminus to membranes containing anionic phospholipids, leading to a lipid-bound intermediate. This interaction induces a conformational change in SecA, resulting in a high-affinity association with SecYEG, which initiates protein translocation. Here, we examined the effect of anionic lipids on the SecA-SecYEG interaction in more detail, and discovered a second, yet unknown, anionic lipid-dependent event that stimulates protein translocation. Based on molecular dynamics simulations we identified an anionic lipid-enriched region in vicinity of the lateral gate of SecY. Here, the anionic lipid headgroup accesses the lateral gate, thereby stabilizing the pre-open state of the channel. The simulations suggest flip-flop movement of phospholipid along the lateral gate. Electrostatic contribution of the anionic phospholipids at the lateral gate may directly stabilize positively charged residues of the signal sequence of an incoming preprotein. Such a mechanism allows for the correct positioning of the entrant peptide, thereby providing a long-sought explanation for the role of anionic lipids in signal sequence folding during protein translocation.
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Affiliation(s)
- Sabrina Koch
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands.
| | - Marten Exterkate
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands.
| | - Cesar A López
- Department of Molecular Dynamics, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands; Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, NM, USA.
| | - Megha Patro
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands.
| | - Siewert J Marrink
- Department of Molecular Dynamics, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands.
| | - Arnold J M Driessen
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, the Netherlands.
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13
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Hoffmann B, Löhr F, Laguerre A, Bernhard F, Dötsch V. Protein labeling strategies for liquid-state NMR spectroscopy using cell-free synthesis. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2018; 105:1-22. [PMID: 29548364 DOI: 10.1016/j.pnmrs.2017.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 05/17/2023]
Abstract
Preparation of a protein sample for liquid-state nuclear magnetic resonance (NMR) spectroscopy analysis requires optimization of many parameters. This review describes labeling strategies for obtaining assignments of protein resonances. Particular emphasis is placed on the advantages of cell-free protein production, which enables exclusive labeling of the protein of interest, thereby simplifying downstream processing steps and increasing the availability of different labeling strategies for a target protein. Furthermore, proteins can be synthesized in milligram yields, and the open nature of the cell-free system allows the addition of stabilizers, scrambling inhibitors or hydrophobic solubilization environments directly during the protein synthesis, which is especially beneficial for membrane proteins. Selective amino acid labeling of the protein of interest, the possibility of addressing scrambling issues and avoiding the need for labile amino acid precursors have been key factors in enabling the introduction of new assignment strategies based on different labeling schemes as well as on new pulse sequences. Combinatorial selective labeling methods have been developed to reduce the number of protein samples necessary to achieve a complete backbone assignment. Furthermore, selective labeling helps to decrease spectral overlap and overcome size limitations for solution NMR analysis of larger complexes, oligomers, intrinsically disordered proteins and membrane proteins.
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Affiliation(s)
- Beate Hoffmann
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| | - Frank Löhr
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| | - Aisha Laguerre
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| | - Frank Bernhard
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue Str. 9, 60438 Frankfurt, Germany.
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14
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Chen Y, Bensing BA, Seepersaud R, Mi W, Liao M, Jeffrey PD, Shajahan A, Sonon RN, Azadi P, Sullam PM, Rapoport TA. Unraveling the sequence of cytosolic reactions in the export of GspB adhesin from Streptococcus gordonii. J Biol Chem 2018; 293:5360-5373. [PMID: 29462788 DOI: 10.1074/jbc.ra117.000963] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/05/2018] [Indexed: 12/24/2022] Open
Abstract
Many pathogenic bacteria, including Streptococcus gordonii, possess a pathway for the cellular export of a single serine-rich-repeat protein that mediates the adhesion of bacteria to host cells and the extracellular matrix. This adhesin protein is O-glycosylated by several cytosolic glycosyltransferases and requires three accessory Sec proteins (Asp1-3) for export, but how the adhesin protein is processed for export is not well understood. Here, we report that the S. gordonii adhesin GspB is sequentially O-glycosylated by three enzymes (GtfA/B, Nss, and Gly) that attach N-acetylglucosamine and glucose to Ser/Thr residues. We also found that modified GspB is transferred from the last glycosyltransferase to the Asp1/2/3 complex. Crystal structures revealed that both Asp1 and Asp3 are related to carbohydrate-binding proteins, suggesting that they interact with carbohydrates and bind glycosylated adhesin, a notion that was supported by further analyses. We further observed that Asp1 also has an affinity for phospholipids, which is attenuated by Asp2. In summary, our findings support a model in which the GspB adhesin is sequentially glycosylated by GtfA/B, Nss, and Gly and then transferred to the Asp1/2/3 complex in which Asp1 mediates the interaction of the Asp1/2/3 complex with the lipid bilayer for targeting of matured GspB to the export machinery.
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Affiliation(s)
- Yu Chen
- From the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Barbara A Bensing
- the Department of Medicine, San Francisco Veteran Affairs Medical Center, University of California at San Francisco, San Francisco, California 94121
| | - Ravin Seepersaud
- the Department of Medicine, San Francisco Veteran Affairs Medical Center, University of California at San Francisco, San Francisco, California 94121
| | - Wei Mi
- From the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Maofu Liao
- From the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Philip D Jeffrey
- the Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
| | - Asif Shajahan
- the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Roberto N Sonon
- the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Parastoo Azadi
- the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Paul M Sullam
- the Department of Medicine, San Francisco Veteran Affairs Medical Center, University of California at San Francisco, San Francisco, California 94121
| | - Tom A Rapoport
- From the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, .,the Howard Hughes Medical Institute, Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
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15
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Sendecki AM, Poyton MF, Baxter AJ, Yang T, Cremer PS. Supported Lipid Bilayers with Phosphatidylethanolamine as the Major Component. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13423-13429. [PMID: 29119796 DOI: 10.1021/acs.langmuir.7b02323] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Phosphatidylethanolamine (PE) is notoriously difficult to incorporate into model membrane systems, such as fluid supported lipid bilayers (SLBs), at high concentrations because of its intrinsic negative curvature. Using fluorescence-based techniques, we demonstrate that having fewer sites of unsaturation in the lipid tails leads to high-quality SLBs because these lipids help to minimize the curvature. Moreover, shorter saturated chains can help maintain the membranes in the fluid phase. Using these two guidelines, we find that up to 70 mol % PE can be incorporated into SLBs at room temperature and up to 90 mol % PE can be incorporated at 37 °C. Curiously, conditions under which three-dimensional tubules project outward from the planar surface as well as conditions under which domain formation occurs can be found. We have employed these model membrane systems to explore the ability of Ni2+ to bind to PE. It was found that this transition metal ion binds 1000-fold tighter to PE than to phosphatidylcholine lipids. In the future, this platform could be exploited to monitor the binding of other transition metal ions or the binding of antimicrobial peptides. It could also be employed to explore the physical properties of PE-containing membranes, such as phase domain behavior and intermolecular hydrogen bonding.
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Affiliation(s)
- Anne M Sendecki
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Matthew F Poyton
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Alexis J Baxter
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Tinglu Yang
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Paul S Cremer
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
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16
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Crane JM, Randall LL. The Sec System: Protein Export in Escherichia coli. EcoSal Plus 2017; 7:10.1128/ecosalplus.ESP-0002-2017. [PMID: 29165233 PMCID: PMC5807066 DOI: 10.1128/ecosalplus.esp-0002-2017] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 11/20/2022]
Abstract
In Escherichia coli, proteins found in the periplasm or the outer membrane are exported from the cytoplasm by the general secretory, Sec, system before they acquire stably folded structure. This dynamic process involves intricate interactions among cytoplasmic and membrane proteins, both peripheral and integral, as well as lipids. In vivo, both ATP hydrolysis and proton motive force are required. Here, we review the Sec system from the inception of the field through early 2016, including biochemical, genetic, and structural data.
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Affiliation(s)
- Jennine M. Crane
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, Missouri
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17
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Miller DM, Findlay HE, Ces O, Templer RH, Booth PJ. Light-activated control of protein channel assembly mediated by membrane mechanics. NANOTECHNOLOGY 2016; 27:494004. [PMID: 27831930 DOI: 10.1088/0957-4484/27/49/494004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Photochemical processes provide versatile triggers of chemical reactions. Here, we use a photoactivated lipid switch to modulate the folding and assembly of a protein channel within a model biological membrane. In contrast to the information rich field of water-soluble protein folding, there is only a limited understanding of the assembly of proteins that are integral to biological membranes. It is however possible to exploit the foreboding hydrophobic lipid environment and control membrane protein folding via lipid bilayer mechanics. Mechanical properties such as lipid chain lateral pressure influence the insertion and folding of proteins in membranes, with different stages of folding having contrasting sensitivities to the bilayer properties. Studies to date have relied on altering bilayer properties through lipid compositional changes made at equilibrium, and thus can only be made before or after folding. We show that light-activation of photoisomerisable di-(5-[[4-(4-butylphenyl)azo]phenoxy]pentyl)phosphate (4-Azo-5P) lipids influences the folding and assembly of the pentameric bacterial mechanosensitive channel MscL. The use of a photochemical reaction enables the bilayer properties to be altered during folding, which is unprecedented. This mechanical manipulation during folding, allows for optimisation of different stages of the component insertion, folding and assembly steps within the same lipid system. The photochemical approach offers the potential to control channel assembly when generating synthetic devices that exploit the mechanosensitive protein as a nanovalve.
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Affiliation(s)
- David M Miller
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia. Department of Medical Biology, The University of Melbourne, 3052, Australia
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18
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Ohta N, Kato Y, Watanabe H, Mori H, Matsuura T. In vitro membrane protein synthesis inside Sec translocon-reconstituted cell-sized liposomes. Sci Rep 2016; 6:36466. [PMID: 27808179 PMCID: PMC5093552 DOI: 10.1038/srep36466] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 10/17/2016] [Indexed: 12/24/2022] Open
Abstract
Protein synthesis using an in vitro transcription-translation system (IVTT) inside cell-sized liposomes has become a valuable tool to study the properties of biological systems under cell-mimicking conditions. However, previous liposome systems lacked the machinery for membrane protein translocation. Here, we reconstituted the translocon consisting of SecYEG from Escherichia coli inside cell-sized liposomes. The cell-sized liposomes also carry the reconstituted IVTT, thereby providing a cell-mimicking environment for membrane protein synthesis. By using EmrE, a multidrug transporter from E. coli, as a model membrane protein, we found that both the amount and activity of EmrE synthesized inside the liposome is increased approximately three-fold by incorporating the Sec translocon. The topological change of EmrE induced by the translocon was also identified. The membrane integration of 6 out of 9 E. coli inner membrane proteins that was tested was increased by incorporation of the translocon. By introducing the Sec translocon, the membrane integration efficiency of the membrane protein of interest was increased, and enabled the integration of membrane proteins that otherwise cannot be inserted. In addition, this work represents an essential step toward the construction of an artificial cell through a bottom-up approach.
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Affiliation(s)
- Naoki Ohta
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan
| | - Yasuhiko Kato
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan
| | - Hajime Watanabe
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan
| | - Hirotada Mori
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama-tyou, Ikoma, Nara, Japan
| | - Tomoaki Matsuura
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan
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19
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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.
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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
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20
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Theis J, Schroda M. Revisiting the photosystem II repair cycle. PLANT SIGNALING & BEHAVIOR 2016; 11:e1218587. [PMID: 27494214 PMCID: PMC5058467 DOI: 10.1080/15592324.2016.1218587] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 07/23/2016] [Accepted: 07/25/2016] [Indexed: 05/18/2023]
Abstract
The ability of photosystem (PS) II to catalyze the light-driven oxidation of water comes along with its vulnerability to oxidative damage, in particular of the D1 core subunit. Photodamaged PSII undergoes repair in a multi-step process involving (i) reversible phosphorylation of PSII core subunits; (ii) monomerization and lateral migration of the PSII core from grana to stroma thylakoids; (iii) partial disassembly of PSII; (iv) proteolytic degradation of damaged D1; (v) replacement of damaged D1 protein with a new copy; (vi) reassembly of PSII monomers and migration back to grana thylakoids for dimerization and supercomplex assembly. Here we review the current knowledge on the PSII repair cycle.
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Affiliation(s)
- Jasmine Theis
- Molekulare Biotechnologie & Systembiologie, TU Kaiserslautern, Kaiserslautern, Germany
| | - Michael Schroda
- Molekulare Biotechnologie & Systembiologie, TU Kaiserslautern, Kaiserslautern, Germany
- CONTACT Michael Schroda Molekulare Biotechnologie & Systembiologie, TU Kaiserslautern, Paul-Ehrlich-Str. 70, 67663 Kaiserslautern, Germany
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21
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Hresko RC, Kraft TE, Quigley A, Carpenter EP, Hruz PW. Mammalian Glucose Transporter Activity Is Dependent upon Anionic and Conical Phospholipids. J Biol Chem 2016; 291:17271-82. [PMID: 27302065 PMCID: PMC5016126 DOI: 10.1074/jbc.m116.730168] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Indexed: 01/05/2023] Open
Abstract
The regulated movement of glucose across mammalian cell membranes is mediated by facilitative glucose transporters (GLUTs) embedded in lipid bilayers. Despite the known importance of phospholipids in regulating protein structure and activity, the lipid-induced effects on the GLUTs remain poorly understood. We systematically examined the effects of physiologically relevant phospholipids on glucose transport in liposomes containing purified GLUT4 and GLUT3. The anionic phospholipids, phosphatidic acid, phosphatidylserine, phosphatidylglycerol, and phosphatidylinositol, were found to be essential for transporter function by activating it and stabilizing its structure. Conical lipids, phosphatidylethanolamine and diacylglycerol, enhanced transporter activity up to 3-fold in the presence of anionic phospholipids but did not stabilize protein structure. Kinetic analyses revealed that both lipids increase the kcat of transport without changing the Km values. These results allowed us to elucidate the activation of GLUT by plasma membrane phospholipids and to extend the field of membrane protein-lipid interactions to the family of structurally and functionally related human solute carriers.
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Affiliation(s)
| | | | - Andrew Quigley
- the Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Elisabeth P Carpenter
- the Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Paul W Hruz
- From the Departments of Pediatrics and Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110 and
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22
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Prabudiansyah I, Kusters I, Caforio A, Driessen AJ. Characterization of the annular lipid shell of the Sec translocon. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2050-6. [DOI: 10.1016/j.bbamem.2015.06.024] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/24/2015] [Accepted: 06/26/2015] [Indexed: 11/16/2022]
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23
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Biology and Assembly of the Bacterial Envelope. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 883:41-76. [PMID: 26621461 DOI: 10.1007/978-3-319-23603-2_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
All free-living bacterial cells are delimited and protected by an envelope of high complexity. This physiological barrier is essential for bacterial survival and assures multiple functions. The molecular assembly of the different envelope components into a functional structure represents a tremendous biological challenge and is of high interest for fundamental sciences. The study of bacterial envelope assembly has also been fostered by the need for novel classes of antibacterial agents to fight the problematic of bacterial resistance to antibiotics. This chapter focuses on the two most intensively studied classes of bacterial envelopes that belong to the phyla Firmicutes and Proteobacteria. The envelope of Firmicutes typically has one membrane and is defined as being monoderm whereas the envelope of Proteobacteria contains two distinct membranes and is referred to as being diderm. In this chapter, we will first discuss the multiple roles of the bacterial envelope and clarify the nomenclature used to describe the different types of envelopes. We will then define the architecture and composition of the envelopes of Firmicutes and Proteobacteria while outlining their similarities and differences. We will further cover the extensive progress made in the field of bacterial envelope assembly over the last decades, using Bacillus subtilis and Escherichia coli as model systems for the study of the monoderm and diderm bacterial envelopes, respectively. We will detail our current understanding of how molecular machines assure the secretion, insertion and folding of the envelope proteins as well as the assembly of the glycosidic components of the envelope. Finally, we will highlight the topics that are still under investigation, and that will surely lead to important discoveries in the near future.
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24
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Folding energetics and oligomerization of polytopic α-helical transmembrane proteins. Arch Biochem Biophys 2014; 564:281-96. [DOI: 10.1016/j.abb.2014.07.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 06/26/2014] [Accepted: 07/14/2014] [Indexed: 01/06/2023]
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25
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Denks K, Vogt A, Sachelaru I, Petriman NA, Kudva R, Koch HG. The Sec translocon mediated protein transport in prokaryotes and eukaryotes. Mol Membr Biol 2014; 31:58-84. [DOI: 10.3109/09687688.2014.907455] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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26
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Chatzi KE, Sardis MF, Economou A, Karamanou S. SecA-mediated targeting and translocation of secretory proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1466-74. [PMID: 24583121 DOI: 10.1016/j.bbamcr.2014.02.014] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/12/2014] [Accepted: 02/15/2014] [Indexed: 11/26/2022]
Abstract
More than 30 years of research have revealed that the dynamic nanomotor SecA is a central player in bacterial protein secretion. SecA associates with the SecYEG channel and transports polypeptides post-translationally to the trans side of the cytoplasmic membrane. It comprises a helicase-like ATPase core coupled to two domains that provide specificity for preprotein translocation. Apart from SecYEG, SecA associates with multiple ligands like ribosomes, nucleotides, lipids, chaperones and preproteins. It exerts its essential contribution in two phases. First, SecA, alone or in concert with chaperones, helps mediate the targeting of the secretory proteins from the ribosome to the membrane. Next, at the membrane it converts chemical energy to mechanical work and translocates preproteins through the SecYEG channel. SecA is a highly dynamic enzyme, it exploits disorder-order kinetics, swiveling and dissociation of domains and dimer to monomer transformations that are tightly coupled with its catalytic function. Preprotein signal sequences and mature domains exploit these dynamics to manipulate the nanomotor and thus achieve their export at the expense of metabolic energy. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Katerina E Chatzi
- Institute of Molecular Biology and Biotechnology, FORTH, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece; KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Molecular Bacteriology, 3000 Leuven, Belgium
| | - Marios Frantzeskos Sardis
- KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Molecular Bacteriology, 3000 Leuven, Belgium
| | - Anastassios Economou
- Institute of Molecular Biology and Biotechnology, FORTH, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece; Department of Biology, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece; KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Molecular Bacteriology, 3000 Leuven, Belgium.
| | - Spyridoula Karamanou
- Institute of Molecular Biology and Biotechnology, FORTH, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece; KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Molecular Bacteriology, 3000 Leuven, Belgium.
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27
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Rütgers M, Schroda M. A role of VIPP1 as a dynamic structure within thylakoid centers as sites of photosystem biogenesis? PLANT SIGNALING & BEHAVIOR 2013; 8:e27037. [PMID: 24300099 PMCID: PMC4091218 DOI: 10.4161/psb.27037] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 11/01/2013] [Accepted: 11/01/2013] [Indexed: 05/19/2023]
Abstract
The vesicle inducing protein in plastids (VIPP1) is an essential protein for the biogenesis of thylakoids in modern cyanobacteria, algae, and plants. Although its exact function is still not clear, recent work has provided important hints to its mode of action. We believe that these data are consistent with a structural role of VIPP1 within thylakoid centers, which are considered as sites from which thylakoid membranes emerge and at which the biogenesis at least of photosystem II is thought to occur. Here we present a model that may serve as starting point for future research.
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28
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Taufik I, Kedrov A, Exterkate M, Driessen AJ. Monitoring the Activity of Single Translocons. J Mol Biol 2013; 425:4145-53. [DOI: 10.1016/j.jmb.2013.08.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/12/2013] [Accepted: 08/14/2013] [Indexed: 10/26/2022]
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29
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Kedrov A, Kusters I, Driessen AJM. Single-Molecule Studies of Bacterial Protein Translocation. Biochemistry 2013; 52:6740-54. [DOI: 10.1021/bi400913x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Alexej Kedrov
- Department of Molecular Microbiology, Groningen
Biomolecular Sciences and Biotechnology Institute, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747
AG Groningen, The Netherlands
| | - Ilja Kusters
- Department of Molecular Microbiology, Groningen
Biomolecular Sciences and Biotechnology Institute, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747
AG Groningen, The Netherlands
| | - Arnold J. M. Driessen
- Department of Molecular Microbiology, Groningen
Biomolecular Sciences and Biotechnology Institute, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747
AG Groningen, The Netherlands
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30
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You Z, Liao M, Zhang H, Yang H, Pan X, Houghton JE, Sui SF, Tai PC. Phospholipids induce conformational changes of SecA to form membrane-specific domains: AFM structures and implication on protein-conducting channels. PLoS One 2013; 8:e72560. [PMID: 23977317 PMCID: PMC3745498 DOI: 10.1371/journal.pone.0072560] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 07/12/2013] [Indexed: 11/23/2022] Open
Abstract
SecA, an essential component of the Sec machinery, exists in a soluble and a membrane form in Escherichia coli. Previous studies have shown that the soluble SecA transforms into pore structures when it interacts with liposomes, and integrates into membranes containing SecYEG in two forms: SecAS and SecAM; the latter exemplified by two tryptic membrane-specific domains, an N-terminal domain (N39) and a middle M48 domain (M48). The formation of these lipid-specific domains was further investigated. The N39 and M48 domains are induced only when SecA interacts with anionic liposomes. Additionally, the N-terminus, not the C-terminus of SecA is required for inducing such conformational changes. Proteolytic treatment and sequence analyses showed that liposome-embedded SecA yields the same M48 and N39 domains as does the membrane-embedded SecA. Studies with chemical extraction and resistance to trypsin have also shown that these proteoliposome-embedded SecA fragments exhibit the same stability and characteristics as their membrane-embedded SecA equivalents. Furthermore, the cloned lipid-specific domains N39 and M48, but not N68 or C34, are able to form partial, but imperfect ring-like structures when they interact with phospholipids. These ring-like structures are characteristic of a SecA pore-structure, suggesting that these domains contribute part of the SecA-dependent protein-conducting channel. We, therefore, propose a model in which SecA alone is capable of forming a lipid-specific, asymmetric dimer that is able to function as a viable protein-conducting channel in the membrane, without any requirement for SecYEG.
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Affiliation(s)
- Zhipeng You
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
| | - Meijiang Liao
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
| | - Hao Zhang
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
| | - Hsiuchin Yang
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
| | - Xijian Pan
- School of Life Sciences, Center for Structural Biology, Tsinghua University, Beijing, China
| | - John E. Houghton
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
| | - Sen-fang Sui
- School of Life Sciences, Center for Structural Biology, Tsinghua University, Beijing, China
| | - Phang C. Tai
- Department of Biology and Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, United States of America
- * E-mail:
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Becker T, Horvath SE, Böttinger L, Gebert N, Daum G, Pfanner N. Role of phosphatidylethanolamine in the biogenesis of mitochondrial outer membrane proteins. J Biol Chem 2013; 288:16451-16459. [PMID: 23625917 PMCID: PMC3675581 DOI: 10.1074/jbc.m112.442392] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 04/19/2013] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial outer membrane contains proteinaceous machineries for the import and assembly of proteins, including TOM (translocase of the outer membrane) and SAM (sorting and assembly machinery). It has been shown that the dimeric phospholipid cardiolipin is required for the stability of TOM and SAM complexes and thus for the efficient import and assembly of β-barrel proteins and some α-helical proteins of the outer membrane. Here, we report that mitochondria deficient in phosphatidylethanolamine (PE), the second non-bilayer-forming phospholipid, are impaired in the biogenesis of β-barrel proteins, but not of α-helical outer membrane proteins. The stability of TOM and SAM complexes is not disturbed by the lack of PE. By dissecting the import steps of β-barrel proteins, we show that an early import stage involving translocation through the TOM complex is affected. In PE-depleted mitochondria, the TOM complex binds precursor proteins with reduced efficiency. We conclude that PE is required for the proper function of the TOM complex.
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Affiliation(s)
- Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany
| | - Susanne E Horvath
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany; Institut für Biochemie, Technische Universität Graz, A-8010 Graz, Austria
| | - Lena Böttinger
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Natalia Gebert
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany
| | - Günther Daum
- Institut für Biochemie, Technische Universität Graz, A-8010 Graz, Austria.
| | - Nikolaus Pfanner
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany.
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32
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Abstract
Temperature sensing is essential for the survival of living cells. The membrane-bound thermosensor DesK from Bacillus subtilis is a key representative of histidine kinases receptors able to remodel membrane lipid composition when the temperature drops below ~30°C. Although the receptor is well studied, a central issue remains: how does the compositional and functional diversity of the surrounding membrane modulate receptor function? Reconstituting full-length DesK into proteoliposomes of well-defined and controlled lipid composition represents a minimal synthetic approach to systematically address this question. Thus DesK has been reconstituted in a variety of phospholipid bilayers and its temperature-regulated autokinase activity determined as function of fatty acyl chain length, lipid head-group structure and phase preference. We show that the head group structure of lipids (both in vitro and in vivo) has little effect on DesK thermosensing, whereas properties determined by the acyl chain of lipids, such as membrane thickness and phase separation into coexisting lipid domains, exert a profound regulatory effect on kinase domain activation at low temperatures. These experiments suggest that the non-polar domain of glycerolipids is essential to regulate the allosteric structural transitions of DesK, by activating the autophosphorylation of the intracellular kinase domain in response to a decrease in temperature.
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33
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Influence of lipids on protein-mediated transmembrane transport. Chem Phys Lipids 2013; 169:57-71. [PMID: 23473882 DOI: 10.1016/j.chemphyslip.2013.02.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Revised: 02/20/2013] [Accepted: 02/25/2013] [Indexed: 02/04/2023]
Abstract
Transmembrane proteins are responsible for transporting ions and small molecules across the hydrophobic region of the cell membrane. We are reviewing the evidence for regulation of these transport processes by interactions with the lipids of the membrane. We focus on ion channels, including potassium channels, mechanosensitive and pentameric ligand gated ion channels, and active transporters, including pumps, sodium or proton driven secondary transporters and ABC transporters. For ion channels it has been convincingly shown that specific lipid-protein interactions can directly affect their function. In some cases, a combined approach of molecular and structural biology together with computer simulations has revealed the molecular mechanisms. There are also many transporters whose activity depends on lipids but understanding of the molecular mechanisms is only beginning.
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34
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Yin LM, Edwards MA, Li J, Yip CM, Deber CM. Roles of hydrophobicity and charge distribution of cationic antimicrobial peptides in peptide-membrane interactions. J Biol Chem 2012; 287:7738-45. [PMID: 22253439 DOI: 10.1074/jbc.m111.303602] [Citation(s) in RCA: 284] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cationic antimicrobial peptides (CAPs) occur as important innate immunity agents in many organisms, including humans, and offer a viable alternative to conventional antibiotics, as they physically disrupt the bacterial membranes, leading to membrane lysis and eventually cell death. In this work, we studied the biophysical and microbiological characteristics of designed CAPs varying in hydrophobicity levels and charge distributions by a variety of biophysical and biochemical approaches, including in-tandem atomic force microscopy, attenuated total reflection-FTIR, CD spectroscopy, and SDS-PAGE. Peptide structural properties were correlated with their membrane-disruptive abilities and antimicrobial activities. In bacterial lipid model membranes, a time-dependent increase in aggregated β-strand-type structure in CAPs with relatively high hydrophobicity (such as KKKKKKALFALWLAFLA-NH(2)) was essentially absent in CAPs with lower hydrophobicity (such as KKKKKKAAFAAWAAFAA-NH(2)). Redistribution of positive charges by placing three Lys residues at both termini while maintaining identical sequences minimized self-aggregation above the dimer level. Peptides containing four Leu residues were destructive to mammalian model membranes, whereas those with corresponding Ala residues were not. This finding was mirrored in hemolysis studies in human erythrocytes, where Ala-only peptides displayed virtually no hemolysis up to 320 μM, but the four-Leu peptides induced 40-80% hemolysis at the same concentration range. All peptides studied displayed strong antimicrobial activity against Pseudomonas aeruginosa (minimum inhibitory concentrations of 4-32 μM). The overall findings suggest optimum routes to balancing peptide hydrophobicity and charge distribution that allow efficient penetration and disruption of the bacterial membranes without damage to mammalian (host) membranes.
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Affiliation(s)
- Lois M Yin
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Canada
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35
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A single copy of SecYEG is sufficient for preprotein translocation. EMBO J 2011; 30:4387-97. [PMID: 21897368 DOI: 10.1038/emboj.2011.314] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 07/15/2011] [Indexed: 11/08/2022] Open
Abstract
The heterotrimeric SecYEG complex comprises a protein-conducting channel in the bacterial cytoplasmic membrane. SecYEG functions together with the motor protein SecA in preprotein translocation. Here, we have addressed the functional oligomeric state of SecYEG when actively engaged in preprotein translocation. We reconstituted functional SecYEG complexes labelled with fluorescent markers into giant unilamellar vesicles at a natively low density. Förster's resonance energy transfer and fluorescence (cross-) correlation spectroscopy with single-molecule sensitivity allowed for independent observations of the SecYEG and preprotein dynamics, as well as complex formation. In the presence of ATP and SecA up to 80% of the SecYEG complexes were loaded with a preprotein translocation intermediate. Neither the interaction with SecA nor preprotein translocation resulted in the formation of SecYEG oligomers, whereas such oligomers can be detected when enforced by crosslinking. These data imply that the SecYEG monomer is sufficient to form a functional translocon in the lipid membrane.
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36
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Yano Y, Yamamoto A, Ogura M, Matsuzaki K. Thermodynamics of Insertion and Self-Association of a Transmembrane Helix: A Lipophobic Interaction by Phosphatidylethanolamine. Biochemistry 2011; 50:6806-14. [DOI: 10.1021/bi200560c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yoshiaki Yano
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Sakyo-ku, Kyoto
606-8501, Japan
| | - Arisa Yamamoto
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Sakyo-ku, Kyoto
606-8501, Japan
| | - Mai Ogura
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Sakyo-ku, Kyoto
606-8501, Japan
| | - Katsumi Matsuzaki
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Sakyo-ku, Kyoto
606-8501, Japan
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37
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The potassium channel KcsA: a model protein in studying membrane protein oligomerization and stability of oligomeric assembly? Arch Biochem Biophys 2011; 510:1-10. [PMID: 21458409 DOI: 10.1016/j.abb.2011.03.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Revised: 03/25/2011] [Accepted: 03/25/2011] [Indexed: 01/01/2023]
Abstract
Many membrane proteins are functional as stable oligomers. An understanding of the conditions that elicit and enhance oligomerization is important in many therapeutics. In this regard, protein-protein and protein-lipid interactions play crucial roles in the assembly and stability of oligomeric complexes. Recent years have seen a rapid increase in the mechanistic information on the importance of cytoplasmic termini in determining subunit assembly and stability of oligomeric complexes. In addition, the role of specific protein-lipid interaction between anionic phospholipids and "hot spots" on the protein surface has also become evident in stabilizing oligomeric assemblies. This review focuses on several contemporary developments of membrane proteins that stabilize oligomers by taking the potassium channel KcsA as an exemplary ion channel.
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du Plessis DJF, Nouwen N, Driessen AJM. The Sec translocase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:851-65. [PMID: 20801097 DOI: 10.1016/j.bbamem.2010.08.016] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 08/19/2010] [Accepted: 08/20/2010] [Indexed: 11/18/2022]
Abstract
The vast majority of proteins trafficking across or into the bacterial cytoplasmic membrane occur via the translocon. The translocon consists of the SecYEG complex that forms an evolutionarily conserved heterotrimeric protein-conducting membrane channel that functions in conjunction with a variety of ancillary proteins. For posttranslational protein translocation, the translocon interacts with the cytosolic motor protein SecA that drives the ATP-dependent stepwise translocation of unfolded polypeptides across the membrane. For the cotranslational integration of membrane proteins, the translocon interacts with ribosome-nascent chain complexes and membrane insertion is coupled to polypeptide chain elongation at the ribosome. These processes are assisted by the YidC and SecDF(yajC) complex that transiently interacts with the translocon. This review summarizes our current understanding of the structure-function relationship of the translocon and its interactions with ancillary components during protein translocation and membrane protein insertion. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- David J F du Plessis
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Zernike Institute for Advanced Materials, University of Groningen, 9751NN Haren, The Netherlands
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39
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Oreopoulos J, Yip CM. Combinatorial microscopy for the study of protein–membrane interactions in supported lipid bilayers: Order parameter measurements by combined polarized TIRFM/AFM. J Struct Biol 2009; 168:21-36. [DOI: 10.1016/j.jsb.2009.02.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 02/23/2009] [Accepted: 02/24/2009] [Indexed: 02/06/2023]
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40
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Teixeira PCN, de Souza CAM, de Freitas MS, Foguel D, Caffarena ER, Alves LA. Predictions suggesting a participation of beta-sheet configuration in the M2 domain of the P2X(7) receptor: a novel conformation? Biophys J 2009; 96:951-63. [PMID: 19186133 DOI: 10.1016/j.bpj.2008.10.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 10/15/2008] [Indexed: 11/18/2022] Open
Abstract
Scanning experiments have shown that the putative TM2 domain of the P2X(7) receptor (P2X(7)R) lines the ionic pore. However, none has identified an alpha-helix structure, the paradigmatic secondary structure of ion channels in mammalian cells. In addition, some researchers have suggested a beta-sheet conformation in the TM2 domain of P2X(2). These data led us to investigate a new architecture within the P2X receptor family. P2X(7)R is considered an intriguing receptor because its activation induces nonselective large pore formation, in contrast to the majority of other ionic channel proteins in mammals. This receptor has two states: a low-conductance channel (approximately 10 pS) and a large pore (> 400 pS). To our knowledge, one fundamental question remains unanswered: Are the P2X(7)R channel and the pore itself the same entity or are they different structures? There are no structural data to help solve this question. Thus, we investigated the hydrophobic M2 domain with the aim of predicting the fitted position and the secondary structure of the TM2 segment from human P2X(7)R (hP2X(7)R). We provide evidence for a beta-sheet conformation, using bioinformatics algorithms and molecular-dynamics simulation in conjunction with circular dichroism in different environments and Fourier transform infrared spectroscopy. In summary, our study suggests the possibility that a segment composed of residues from part of the M2 domain and part of the putative TM2 segment of P2X(7)R is partially folded in a beta-sheet conformation, and may play an important role in channel/pore formation associated with P2X(7)R activation. It is important to note that most nonselective large pores have a transmembrane beta-sheet conformation. Thus, this study may lead to a paradigmatic change in the P2X(7)R field and/or raise new questions about this issue.
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41
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Wikström M, Kelly AA, Georgiev A, Eriksson HM, Klement MR, Bogdanov M, Dowhan W, Wieslander A. Lipid-engineered Escherichia coli membranes reveal critical lipid headgroup size for protein function. J Biol Chem 2009; 284:954-65. [PMID: 18981182 PMCID: PMC2613627 DOI: 10.1074/jbc.m804482200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 10/23/2008] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli membranes have a substantial bilayer curvature stress due to a large fraction of the nonbilayer-prone lipid phosphatidylethanolamine, and a mutant (AD93) lacking this lipid is severely crippled in several membrane-associated processes. Introduction of four lipid glycosyltransferases from Acholeplasma laidlawii and Arabidopsis thaliana, synthesizing large amounts of two nonbilayer-prone, and two bilayer-forming gluco- and galacto-lipids, (i) restored the curvature stress with the two nonbilayer lipids, and (ii) diluted the high negative lipid surface charge in all AD93 bilayers. Surprisingly, the bilayer-forming diglucosyl-diacylglycerol was almost as good in improving AD93 membrane processes as the two nonbilayer-prone glucosyl-diacylglycerol and galactosyl-diacylglycerol lipids, strongly suggesting that lipid surface charge dilution by these neutral lipids is very important for E. coli. Increased acyl chain length and unsaturation, plus cardiolipin (nonbilayer-prone) content, were probably also beneficial in the modified strains. However, despite a correct transmembrane topology for the transporter LacY in the diglucosyl-diacylglycerol clone, active transport failed in the absence of a nonbilayer-prone glycolipid. The corresponding digalactosyl-diacylglycerol bilayer lipid did not restore AD93 membrane processes, despite analogous acyl chain and cardiolipin contents. Chain ordering, probed by bis-pyrene lipids, was substantially lower in the digalactosyl-diacylglycerol strain lipids due to its extended headgroup. Hence, a low surface charge density of anionic lipids is important in E. coli membranes, but is inefficient if the headgroup of the diluting lipid is too large. This strongly indicates that a certain magnitude of the curvature stress is crucial for the bilayer in vivo.
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Affiliation(s)
- Malin Wikström
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
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42
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Seddon AM, Lorch M, Ces O, Templer RH, Macrae F, Booth PJ. Phosphatidylglycerol lipids enhance folding of an alpha helical membrane protein. J Mol Biol 2008; 380:548-56. [PMID: 18565344 DOI: 10.1016/j.jmb.2008.05.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 04/07/2008] [Accepted: 05/01/2008] [Indexed: 11/27/2022]
Abstract
Membrane lipids are increasingly being recognised as active participants in biological events. The precise roles that individual lipids or global properties of the lipid bilayer play in the folding of membrane proteins remain to be elucidated, Here, we find a significant effect of phosphatidylglycerol (PG) on the folding of a trimeric alpha helical membrane protein from Escherichia coli diacylglycerol kinase. Both the rate and the yield of folding are increased by increasing the amount of PG in lipid vesicles. Moreover, there is a direct correlation between the increase in yield and the increase in rate; thus, folding becomes more efficient in terms of speed and productivity. This effect of PG seems to be a specific requirement for this lipid, rather than a charge effect. We also find an effect of single-chain lyso lipids in decreasing the rate and yield of folding. We compare this to our previous work in which lyso lipids increased the rate and yield of another membrane protein, bacteriorhodopsin. The contrasting effect of lyso lipids on the two proteins can be explained by the different folding reaction mechanisms and key folding steps involved. Our findings provide information on the lipid determinants of membrane protein folding.
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Affiliation(s)
- Annela M Seddon
- Department of Biochemistry, University of Bristol, Bristol BS8 1TD, UK.
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43
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Choi SU, Bui T, Ho RJY. pH-dependent interactions of indinavir and lipids in nanoparticles and their ability to entrap a solute. J Pharm Sci 2008; 97:931-43. [PMID: 17546665 DOI: 10.1002/jps.21020] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have investigated the ability of lipid-indinavir particles composed of 3-to-1 lipid-drug molar ratio to encapsulate an aqueous marker calcein and anti-HIV drug (3)H-phosphonylmethoxypropyl-adenine (PMPA). Even at a high density of indinavir associated to lipid-indinavir nanoparticles, they form an enclosed lipid membrane that allows encapsulation of calcein and PMPA in an aqueous compartment. At neutral pH, practically all indinavir was incorporated into lipid bilayer and lipid associated indinavir can be dissociated with half-maximum pH recorded between 5.2 and 5.5. pH-Dependent release of indinavir did not influence calcein release significantly. However, pH-dependent release of indinavir affected PMPA release. By lowering pH, PMPA release was enhanced in the presence of indinavir in the lipid bilayer. Collectively, these data indicate that indinavir incorporated in lipid particles provides (1) stable bilayers capable of encapsulating other hydrophilic drugs, (2) ability to dissociate indinavir (which is acid stable) from lipid membranes, by lowering the pH, and (3) enabling enhancement in pH-dependent release of aqueous contents. However, the degree of pH-dependent release could be related to the charge and size of an aqueous molecule.
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Affiliation(s)
- Sung-Up Choi
- Department of Pharmaceutics, University of Washington, Box 357610, Seattle, Washington 98195, USA
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44
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Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA. FEBS Lett 2007; 581:5715-22. [DOI: 10.1016/j.febslet.2007.11.039] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2007] [Revised: 11/09/2007] [Accepted: 11/13/2007] [Indexed: 11/22/2022]
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45
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Abstract
The lipid bilayer component of biological membranes is important for the distribution, organization, and function of bilayer-spanning proteins. This regulation is due to both specific lipid-protein interactions and general bilayer-protein interactions, which modulate the energetics and kinetics of protein conformational transitions, as well as the protein distribution between different membrane compartments. The bilayer regulation of membrane protein function arises from the hydrophobic coupling between the protein's hydrophobic domains and the bilayer hydrophobic core, which causes protein conformational changes that involve the protein/bilayer boundary to perturb the adjacent bilayer. Such bilayer perturbations, or deformations, incur an energetic cost, which for a given conformational change varies as a function of the bilayer material properties (bilayer thickness, intrinsic lipid curvature, and the elastic compression and bending moduli). Protein function therefore is regulated by changes in bilayer material properties, which determine the free-energy changes caused by the protein-induced bilayer deformation. The lipid bilayer thus becomes an allosteric regulator of membrane function.
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Affiliation(s)
- Olaf S Andersen
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10021, USA.
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46
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Rajalahti T, Huang F, Klement MR, Pisareva T, Edman M, Sjöström M, Wieslander A, Norling B. Proteins in different Synechocystis compartments have distinguishing N-terminal features: a combined proteomics and multivariate sequence analysis. J Proteome Res 2007; 6:2420-34. [PMID: 17508731 DOI: 10.1021/pr0605973] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cyanobacteria have a cell envelope consisting of a plasma membrane, a periplasmic space with a peptidoglycan layer, and an outer membrane. A third, separate membrane system, the intracellular thylakoid membranes, is the site for both photosynthesis and respiration. All membranes and luminal spaces have unique protein compositions, which impose an intriguing mechanism for protein sorting of extracytoplasmic proteins due to single sets of translocation protein genes. It is shown here by multivariate sequence analyses of many experimentally identified proteins in Synechocystis, that proteins routed for the different extracytosolic compartments have correspondingly different physicochemical properties in their signal peptide and mature N-terminal segments. The full-length mature sequences contain less significant information. From these multivariate, N-terminal property-profile models for proteins with single experimental localization, proteins with ambiguous localization could, to a large extent, be predicted to a defined compartment. The sequence properties involve amino acids varying especially in volume and polarizability and at certain positions in the sequence segments, in a manner typical for the various compartment classes. Potential means of the cell to recognize the property features are discussed, involving the translocation channels and two Type I signal peptidases with different cellular localization, and charge features at their membrane interfaces.
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Affiliation(s)
- Tarja Rajalahti
- Department of Chemistry, University of Bergen, Bergen, Norway
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47
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Alami M, Dalal K, Lelj-Garolla B, Sligar SG, Duong F. Nanodiscs unravel the interaction between the SecYEG channel and its cytosolic partner SecA. EMBO J 2007; 26:1995-2004. [PMID: 17396152 PMCID: PMC1852787 DOI: 10.1038/sj.emboj.7601661] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 03/02/2007] [Indexed: 11/08/2022] Open
Abstract
The translocon is a membrane-embedded protein assembly that catalyzes protein movement across membranes. The core translocon, the SecYEG complex, forms oligomers, but the protein-conducting channel is at the center of the monomer. Defining the properties of the SecYEG protomer is thus crucial to understand the underlying function of oligomerization. We report here the reconstitution of a single SecYEG complex into nano-scale lipid bilayers, termed Nanodiscs. These water-soluble particles allow one to probe the interactions of the SecYEG complex with its cytosolic partner, the SecA dimer, in a membrane-like environment. The results show that the SecYEG complex triggers dissociation of the SecA dimer, associates only with the SecA monomer and suffices to (pre)-activate the SecA ATPase. Acidic lipids surrounding the SecYEG complex also contribute to the binding affinity and activation of SecA, whereas mutations in the largest cytosolic loop of the SecY subunit, known to abolish the translocation reaction, disrupt both the binding and activation of SecA. Altogether, the results define the fundamental contribution of the SecYEG protomer in the translocation subreactions and illustrate the power of nanoscale lipid bilayers in analyzing the dynamics occurring at the membrane.
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Affiliation(s)
- Meriem Alami
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, Faculty of Medicine, University of British Columbia, British Columbia, Canada
| | - Kush Dalal
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, Faculty of Medicine, University of British Columbia, British Columbia, Canada
| | - Barbara Lelj-Garolla
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, Faculty of Medicine, University of British Columbia, British Columbia, Canada
| | - Stephen G Sligar
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Franck Duong
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, Faculty of Medicine, University of British Columbia, British Columbia, Canada
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3. Tel.: +1 604 822 5975; Fax: +1 604 822 5227; E-mail:
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48
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Kiefer D, Kuhn A. YidC as an essential and multifunctional component in membrane protein assembly. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 259:113-38. [PMID: 17425940 DOI: 10.1016/s0074-7696(06)59003-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Membrane proteins fulfill a number of vital functions in prokaryotic and eukaryotic cells. They are often organized in multicomponent complexes, folded within the membrane bilayer and interacting with the cytoplasmic and periplasmic or external soluble compartments. For the biogenesis of integral membrane proteins, the essential biochemical steps are (1) the insertion and topogenesis of the transmembrane protein segments into the lipid bilayer, (2) the three-dimensional folding of the translocated hydrophilic domains, and (3) the assembly into multimeric complexes. Intensive research has elucidated the basic mechanisms of membrane protein insertion in the homologous translocation machineries of different cellular systems. Whereas the Sec translocation system is found in the endoplasmic reticulum of eukaryotic cells and in the prokaryotic plasma membrane, the YidC-Oxa1 membrane insertase is present in prokaryotic and organellar membranes. This review focuses on the discoveries of the YidC system in bacterial as well as the Oxa1/Alb3 protein family of eukaryotic cells and will particularly emphasize evolutionary aspects.
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Affiliation(s)
- Dorothee Kiefer
- Department of Microbiology, University of Hohenheim, D-70599 Stuttgart, Germany
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49
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Sun C, Rusch SL, Kim J, Kendall DA. Chloroplast SecA and Escherichia coli SecA have distinct lipid and signal peptide preferences. J Bacteriol 2006; 189:1171-5. [PMID: 17142391 PMCID: PMC1797313 DOI: 10.1128/jb.01589-06] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Like prokaryotic Sec-dependent protein transport, chloroplasts utilize SecA. However, we observe distinctive requirements for the stimulation of chloroplast SecA ATPase activity; it is optimally stimulated in the presence of galactolipid and only a small fraction of anionic lipid and by Sec-dependent thylakoid signal peptides but not Escherichia coli signal peptides.
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Affiliation(s)
- Changqi Sun
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269-3125, USA
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50
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Ces O, Mulet X. Physical coupling between lipids and proteins: a paradigm for cellular control. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/sita.200500079] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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