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Atomic Force Microscopy Reveals Complexity Underlying General Secretory System Activity. Int J Mol Sci 2022; 24:ijms24010055. [PMID: 36613499 PMCID: PMC9820662 DOI: 10.3390/ijms24010055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/24/2022] Open
Abstract
The translocation of specific polypeptide chains across membranes is an essential activity for all life forms. The main components of the general secretory (Sec) system of E. coli include integral membrane translocon SecYEG, peripheral ATPase SecA, and SecDF, an ancillary complex that enhances polypeptide secretion by coupling translocation to proton motive force. Atomic force microscopy (AFM), a single-molecule imaging technique, is well suited to unmask complex, asynchronous molecular activities of membrane-associated proteins including those comprising the Sec apparatus. Using AFM, the dynamic structure of membrane-external protein topography of Sec system components can be directly visualized with high spatial-temporal precision. This mini-review is focused on AFM imaging of the Sec system in near-native fluid conditions where activity can be maintained and biochemically verified. Angstrom-scale conformational changes of SecYEG are reported on 100 ms timescales in fluid lipid bilayers. The association of SecA with SecYEG, forming membrane-bound SecYEG/SecA translocases, is directly visualized. Recent work showing topographical aspects of the translocation process that vary with precursor species is also discussed. The data suggests that the Sec system does not employ a single translocation mechanism. We posit that differences in the spatial frequency distribution of hydrophobic content within precursor sequences may be a determining factor in mechanism selection. Precise AFM investigations of active translocases are poised to advance our currently vague understanding of the complicated macromolecular movements underlying protein export across membranes.
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Winkler K, Karner A, Horner A, Hannesschlaeger C, Knyazev D, Siligan C, Zimmermann M, Kuttner R, Pohl P, Preiner J. Interaction of the motor protein SecA and the bacterial protein translocation channel SecYEG in the absence of ATP. NANOSCALE ADVANCES 2020; 2:3431-3443. [PMID: 36134293 PMCID: PMC9418451 DOI: 10.1039/d0na00427h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/27/2020] [Indexed: 06/16/2023]
Abstract
Translocation of many secretory proteins through the bacterial plasma membrane is facilitated by a complex of the SecYEG channel with the motor protein SecA. The ATP-free complex is unstable in detergent, raising the question how SecA may perform several rounds of ATP hydrolysis without being released from the membrane embedded SecYEG. Here we show that dual recognition of (i) SecYEG and (ii) vicinal acidic lipids confers an apparent nanomolar affinity. High-speed atomic force microscopy visualizes the complexes between monomeric SecA and SecYEG as being stable for tens of seconds. These long-lasting events and complementary shorter ones both give rise to single ion channel openings of equal duration. Furthermore, luminescence resonance energy transfer reveals two conformations of the SecYEG-SecA complex that differ in the protrusion depth of SecA's two-helix finger into SecYEG's aqueous channel. Such movement of the finger is in line with the power stroke mechanism of protein translocation.
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Affiliation(s)
- Klemens Winkler
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Andreas Karner
- University of Applied Sciences Upper Austria, TIMED Center 4020 Linz Austria
| | - Andreas Horner
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | | | - Denis Knyazev
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Christine Siligan
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Mirjam Zimmermann
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Roland Kuttner
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Peter Pohl
- Johannes Kepler University Linz, Institute of Biophysics 4020 Linz Austria
| | - Johannes Preiner
- University of Applied Sciences Upper Austria, TIMED Center 4020 Linz Austria
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3
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De Geyter J, Portaliou AG, Srinivasu B, Krishnamurthy S, Economou A, Karamanou S. Trigger factor is a bona fide secretory pathway chaperone that interacts with SecB and the translocase. EMBO Rep 2020; 21:e49054. [PMID: 32307852 DOI: 10.15252/embr.201949054] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 03/09/2020] [Accepted: 03/19/2020] [Indexed: 11/09/2022] Open
Abstract
Bacterial secretory preproteins are translocated across the inner membrane post-translationally by the SecYEG-SecA translocase. Mature domain features and signal peptides maintain preproteins in kinetically trapped, largely soluble, folding intermediates. Some aggregation-prone preproteins require chaperones, like trigger factor (TF) and SecB, for solubility and/or targeting. TF antagonizes the contribution of SecB to secretion by an unknown molecular mechanism. We reconstituted this interaction in vitro and studied targeting and secretion of the model preprotein pro-OmpA. TF and SecB display distinct, unsuspected roles in secretion. Tightly associating TF:pro-OmpA targets the translocase at SecA, but TF prevents pro-OmpA secretion. In solution, SecB binds TF:pro-OmpA with high affinity. At the membrane, when bound to the SecA C-tail, SecB increases TF and TF:pro-OmpA affinities for the translocase and allows pro-OmpA to resume translocation. Our data reveal that TF, a main cytoplasmic folding pathway chaperone, is also a bona fide post-translational secretory chaperone that directly interacts with both SecB and the translocase to mediate regulated protein secretion. Thus, TF links the cytoplasmic folding and secretion chaperone networks.
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Affiliation(s)
- Jozefien De Geyter
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Athina G Portaliou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Bindu Srinivasu
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Srinath Krishnamurthy
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Anastassios Economou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
| | - Spyridoula Karamanou
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, KU Leuven, Leuven, Belgium
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Sanganna Gari RR, Chattrakun K, Marsh BP, Mao C, Chada N, Randall LL, King GM. Direct visualization of the E. coli Sec translocase engaging precursor proteins in lipid bilayers. SCIENCE ADVANCES 2019; 5:eaav9404. [PMID: 31206019 PMCID: PMC6561738 DOI: 10.1126/sciadv.aav9404] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 05/09/2019] [Indexed: 06/09/2023]
Abstract
Escherichia coli exports proteins via a translocase comprising SecA and the translocon, SecYEG. Structural changes of active translocases underlie general secretory system function, yet directly visualizing dynamics has been challenging. We imaged active translocases in lipid bilayers as a function of precursor protein species, nucleotide species, and stage of translocation using atomic force microscopy (AFM). Starting from nearly identical initial states, SecA more readily dissociated from SecYEG when engaged with the precursor of outer membrane protein A as compared to the precursor of galactose-binding protein. For the SecA that remained bound to the translocon, the quaternary structure varied with nucleotide, populating SecA2 primarily with adenosine diphosphate (ADP) and adenosine triphosphate, and the SecA monomer with the transition state analog ADP-AlF3. Conformations of translocases exhibited precursor-dependent differences on the AFM imaging time scale. The data, acquired under near-native conditions, suggest that the translocation process varies with precursor species.
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Affiliation(s)
| | - Kanokporn Chattrakun
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Brendan P. Marsh
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Chunfeng Mao
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Nagaraju Chada
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Gavin M. King
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
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5
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Abstract
Single-molecule studies provide unprecedented details about processes that are difficult to grasp by bulk biochemical assays that yield ensemble-averaged results. One of these processes is the translocation and insertion of proteins across and into the bacterial cytoplasmic membrane. This process is facilitated by the universally conserved secretion (Sec) system, a multi-subunit membrane protein complex that consists of dissociable cytoplasmic targeting components, a molecular motor, a protein-conducting membrane pore, and accessory membrane proteins. Here, we review recent insights into the mechanisms of protein translocation and membrane protein insertion from single-molecule studies.
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Affiliation(s)
- Anne-Bart Seinen
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute; and the Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
- Current affiliation: Biophysics Group, AMOLF, 1098 XG Amsterdam, Netherlands
| | - Arnold J.M. Driessen
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute; and the Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
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6
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Chada N, Chattrakun K, Marsh BP, Mao C, Bariya P, King GM. Single-molecule observation of nucleotide induced conformational changes in basal SecA-ATP hydrolysis. SCIENCE ADVANCES 2018; 4:eaat8797. [PMID: 30397644 PMCID: PMC6200364 DOI: 10.1126/sciadv.aat8797] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/13/2018] [Indexed: 05/06/2023]
Abstract
SecA is the critical adenosine triphosphatase that drives preprotein transport through the translocon, SecYEG, in Escherichia coli. This process is thought to be regulated by conformational changes of specific domains of SecA, but real-time, real-space measurement of these changes is lacking. We use single-molecule atomic force microscopy (AFM) to visualize nucleotide-dependent conformations and conformational dynamics of SecA. Distinct topographical populations were observed in the presence of specific nucleotides. AFM investigations during basal adenosine triphosphate (ATP) hydrolysis revealed rapid, reversible transitions between a compact and an extended state at the ~100-ms time scale. A SecA mutant lacking the precursor-binding domain (PBD) aided interpretation. Further, the biochemical activity of SecA prepared for AFM was confirmed by tracking inorganic phosphate release. We conclude that ATP-driven dynamics are largely due to PBD motion but that other segments of SecA contribute to this motion during the transition state of the ATP hydrolysis cycle.
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Affiliation(s)
- Nagaraju Chada
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Kanokporn Chattrakun
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Brendan P. Marsh
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Chunfeng Mao
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Priya Bariya
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
| | - Gavin M. King
- Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA
- Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA
- Corresponding author.
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7
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Li P, Zhang M, Zou Y, Sun Z, Sun C, Geng Z, Xu W, Wang D. Interaction of heat shock protein 90 B1 (Hsp90B1) with liposome reveals its potential role in protection the integrity of lipid membranes. Int J Biol Macromol 2018; 106:1250-1257. [DOI: 10.1016/j.ijbiomac.2017.08.121] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/16/2017] [Accepted: 08/22/2017] [Indexed: 01/28/2023]
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8
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Karner A, Nimmervoll B, Plochberger B, Klotzsch E, Horner A, Knyazev DG, Kuttner R, Winkler K, Winter L, Siligan C, Ollinger N, Pohl P, Preiner J. Tuning membrane protein mobility by confinement into nanodomains. NATURE NANOTECHNOLOGY 2017; 12:260-266. [PMID: 27842062 PMCID: PMC5734611 DOI: 10.1038/nnano.2016.236] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 09/30/2016] [Indexed: 05/04/2023]
Abstract
High-speed atomic force microscopy (HS-AFM) can be used to visualize function-related conformational changes of single soluble proteins. Similar studies of single membrane proteins are, however, hampered by a lack of suitable flat, non-interacting membrane supports and by high protein mobility. Here we show that streptavidin crystals grown on mica-supported lipid bilayers can be used as porous supports for membranes containing biotinylated lipids. Using SecYEG (protein translocation channel) and GlpF (aquaglyceroporin), we demonstrate that the platform can be used to tune the lateral mobility of transmembrane proteins to any value within the dynamic range accessible to HS-AFM imaging through glutaraldehyde-cross-linking of the streptavidin. This allows HS-AFM to study the conformation or docking of spatially confined proteins, which we illustrate by imaging GlpF at sub-molecular resolution and by observing the motor protein SecA binding to SecYEG.
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Affiliation(s)
- Andreas Karner
- Center for Advanced Bioanalysis GmbH, Gruberstr. 40-42, 4020 Linz, Austria
| | | | - Birgit Plochberger
- Upper Austria University of Applied Sciences, Campus Linz, Garnisonstrasse 21, 4020 Linz, Austria
| | - Enrico Klotzsch
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, Australia
| | - Andreas Horner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Denis G. Knyazev
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Roland Kuttner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Klemens Winkler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Lukas Winter
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Christine Siligan
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Nicole Ollinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
| | - Johannes Preiner
- Center for Advanced Bioanalysis GmbH, Gruberstr. 40-42, 4020 Linz, Austria
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Abstract
There is a consensus in the medical profession of the pressing need for novel antimicrobial agents due to issues related to drug resistance. In practice, solutions to this problem to a large degree lie with the identification of new and vital targets in bacteria and subsequently designing their inhibitors. We consider SecA a very promising antimicrobial target. In this review, we compile and analyze information available on SecA to show that inhibition of SecA has a multitude of consequences. Furthermore, we discuss issues critical to the design and evaluation of SecA inhibitors.
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10
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Wu ZC, de Keyzer J, Kusters I, Driessen AJM. Analysis of the interaction between membrane proteins and soluble binding partners by surface plasmon resonance. Methods Mol Biol 2014; 1033:157-72. [PMID: 23996177 DOI: 10.1007/978-1-62703-487-6_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The interaction between membrane proteins and their (protein) ligands is conventionally investigated by nonequilibrium methods such as co-sedimentation or pull-down assays. Surface Plasmon Resonance can be used to monitor such binding events in real-time using isolated membranes immobilized to a surface providing insights in the kinetics of binding under equilibrium conditions. This application provides a fast, automated way to detect interacting species and to determine the kinetics and affinity (Kd) of the interaction.
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Affiliation(s)
- Zht Cheng Wu
- Department of Molecular Microbiology, University of Groningen, Groningen, The Netherlands
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11
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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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12
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Interaction of Streptococcus mutans YidC1 and YidC2 with translating and nontranslating ribosomes. J Bacteriol 2013; 195:4545-51. [PMID: 23935050 DOI: 10.1128/jb.00792-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The YidC/OxaI/Alb3 family of membrane proteins is involved in the biogenesis of integral membrane proteins in bacteria, mitochondria, and chloroplasts. Gram-positive bacteria often contain multiple YidC paralogs that can be subdivided into two major classes, namely, YidC1 and YidC2. The Streptococcus mutans YidC1 and YidC2 proteins possess C-terminal tails that differ in charges (+9 and + 14) and lengths (33 and 61 amino acids). The longer YidC2 C terminus bears a resemblance to the C-terminal ribosome-binding domain of the mitochondrial OxaI protein and, in contrast to the shorter YidC1 C terminus, can mediate the interaction with mitochondrial ribosomes. These observations have led to the suggestion that YidC1 and YidC2 differ in their abilities to interact with ribosomes. However, the interaction with bacterial translating ribosomes has never been addressed. Here we demonstrate that Escherichia coli ribosomes are able to interact with both YidC1 and YidC2. The interaction is stimulated by the presence of a nascent membrane protein substrate and abolished upon deletion of the C-terminal tail, which also abrogates the YidC-dependent membrane insertion of subunit c of the F1F0-ATPase into the membrane. It is concluded that both YidC1 and YidC2 interact with ribosomes, suggesting that the modes of membrane insertion by these membrane insertases are similar.
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13
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Wu ZC, de Keyzer J, Kedrov A, Driessen AJM. Competitive binding of the SecA ATPase and ribosomes to the SecYEG translocon. J Biol Chem 2012; 287:7885-95. [PMID: 22267723 DOI: 10.1074/jbc.m111.297911] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During co-translational membrane insertion of membrane proteins with large periplasmic domains, the bacterial SecYEG complex needs to interact both with the ribosome and the SecA ATPase. Although the binding sites for SecA and the ribosome overlap, it has been suggested that these ligands can interact simultaneously with SecYEG. We used surface plasmon resonance and fluorescence correlation spectroscopy to examine the interaction of SecA and ribosomes with the SecYEG complex present in membrane vesicles and the purified SecYEG complex present in a detergent-solubilized state or reconstituted into nanodiscs. Ribosome binding to the SecYEG complex is strongly stimulated when the ribosomes are charged with nascent chains of the monotopic membrane protein FtsQ. This binding is competed by an excess of SecA, indicating that binding of SecA and ribosomes to SecYEG is mutually exclusive.
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Affiliation(s)
- Zht Cheng Wu
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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Traffic jam at the bacterial sec translocase: targeting the SecA nanomotor by small-molecule inhibitors. ACTA ACUST UNITED AC 2011; 18:685-98. [PMID: 21700205 DOI: 10.1016/j.chembiol.2011.04.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 04/27/2011] [Accepted: 04/28/2011] [Indexed: 11/20/2022]
Abstract
The rapid rise of drug-resistant bacteria is one of the most serious unmet medical needs facing the world. Despite this increasing problem of antibiotic resistance, the number of different antibiotics available for the treatment of serious infections is dwindling. Therefore, there is an urgent need for new antibacterial drugs, preferably with novel modes of action to potentially avoid cross-resistance with existing antibacterial agents. In recent years, increasing attention has been paid to bacterial protein secretion as a potential antibacterial target. Among the different protein secretion pathways that are present in bacterial pathogens, the general protein secretory (Sec) pathway is widely considered as an attractive target for antibacterial therapy. One of the key components of the Sec pathway is the peripheral membrane ATPase SecA, which provides the energy for the translocation of preproteins across the bacterial cytoplasmic membrane. In this review, we will provide an overview of research efforts on the discovery and development of small-molecule SecA inhibitors. Furthermore, recent advances on the structure and function of SecA and their potential impact on antibacterial drug discovery will be discussed.
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15
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Quaternary structure of SecA in solution and bound to SecYEG probed at the single molecule level. Structure 2011; 19:430-9. [PMID: 21397193 DOI: 10.1016/j.str.2010.12.016] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Revised: 12/17/2010] [Accepted: 12/22/2010] [Indexed: 11/20/2022]
Abstract
Dual-color fluorescence-burst analysis (DCFBA) was applied to measure the quaternary structure and high-affinity binding of the bacterial motor protein SecA to the protein-conducting channel SecYEG reconstituted into lipid vesicles. DCFBA is an equilibrium technique that enables the direct observation and quantification of protein-protein interactions at the single molecule level. SecA binds to SecYEG as a dimer with a nucleotide- and preprotein-dependent dissociation constant. One of the SecA protomers binds SecYEG in a salt-resistant manner, whereas binding of the second protomer is salt sensitive. Because protein translocation is salt sensitive, we conclude that the dimeric state of SecA is required for protein translocation. A structural model for the dimeric assembly of SecA while bound to SecYEG is proposed based on the crystal structures of the Thermotoga maritima SecA-SecYEG and the Escherichia coli SecA dimer.
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16
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Thermodynamics of the protein translocation. Methods Enzymol 2009. [PMID: 21609866 DOI: 10.1016/s0076-6879(09)66012-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Many proteins synthesized in bacteria are secreted from the cytoplasm into the periplasm to function in the cell envelope or in the extracellular medium. The Sec translocase is a primary and evolutionary conserved secretion pathway in bacteria. It catalyzes the translocation of unfolded proteins across the cytoplasmic membrane via the pore-forming SecYEG complex. This process is driven by the proton motive force and ATP hydrolysis facilitated by the SecA motor protein. Current insights in the mechanism of protein translocation are largely based on elaborate multidisciplinary studies performed during the last three decades. To understand the process dynamics, the thermodynamic principles of translocation and the subunit interactions need to be addressed. Isothermal titration calorimetry has been widely applied to study thermodynamics of biological interactions, their stability, and driving forces. Here, we describe the examples that exploit this method to investigate key interactions among components of the Sec translocase and suggest further potential applications of calorimetry.
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17
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Maynard JA, Lindquist NC, Sutherland JN, Lesuffleur A, Warrington AE, Rodriguez M, Oh SH. Surface plasmon resonance for high-throughput ligand screening of membrane-bound proteins. Biotechnol J 2009; 4:1542-58. [PMID: 19918786 PMCID: PMC2790208 DOI: 10.1002/biot.200900195] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Technologies based on surface plasmon resonance (SPR) have allowed rapid, label-free characterization of protein-protein and protein-small molecule interactions. SPR has become the gold standard in industrial and academic settings, in which the interaction between a pair of soluble binding partners is characterized in detail or a library of molecules is screened for binding against a single soluble protein. In spite of these successes, SPR is only beginning to be adapted to the needs of membrane-bound proteins which are difficult to study in situ but represent promising targets for drug and biomarker development. Existing technologies, such as BIAcoreTM, have been adapted for membrane protein analysis by building supported lipid layers or capturing lipid vesicles on existing chips. Newer technologies, still in development, will allow membrane proteins to be presented in native or near-native formats. These include SPR nanopore arrays, in which lipid bilayers containing membrane proteins stably span small pores that are addressable from both sides of the bilayer. Here, we discuss current SPR instrumentation and the potential for SPR nanopore arrays to enable quantitative, high-throughput screening of G protein coupled receptor ligands and applications in basic cellular biology.
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Affiliation(s)
- Jennifer A. Maynard
- Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, 78705
| | - Nathan C. Lindquist
- Department of Electrical and Computer Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | - Jamie N. Sutherland
- Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, 78705
| | - Antoine Lesuffleur
- Department of Electrical and Computer Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | | | - Moses Rodriguez
- Departments of Neurology, Mayo Clinic College of Medicine, Rochester, MN 55905
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455
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18
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McLuskey K, Roszak AW, Zhu Y, Isaacs NW. Crystal structures of all-alpha type membrane proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:723-55. [DOI: 10.1007/s00249-009-0546-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/19/2009] [Accepted: 08/26/2009] [Indexed: 01/05/2023]
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19
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van den Bogaart G, Kusters I, Velásquez J, Mika JT, Krasnikov V, Driessen AJM, Poolman B. Dual-color fluorescence-burst analysis to study pore formation and protein-protein interactions. Methods 2008; 46:123-30. [PMID: 18667165 DOI: 10.1016/j.ymeth.2008.06.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 05/22/2008] [Accepted: 06/27/2008] [Indexed: 10/21/2022] Open
Abstract
Dual-color fluorescence-burst analysis (DCBFA) enables to study leakage of fluorescently labeled (macro) molecules from liposomes that are labeled with a second, spectrally non-overlapping fluorophore. The fluorescent bursts that reside from the liposomes diffusing through the focal volume of a confocal microscope will coincide with those from the encapsulated size-marker molecules. The internal concentration of size-marker molecules can be quantitatively calculated from the fluorescence bursts at a single liposome level. DCFBA has been successfully used to study the effective pore-size of the mechanosensitive channel of large-conductance MscL and the pore-forming mechanism of the antimicrobial peptide melittin from bee venom. In addition, DCFBA can be used to quantitatively measure the binding of proteins to liposomes and to membrane proteins. In this paper, we provide an overview of the method and discuss the experimental details of DCFBA.
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Affiliation(s)
- Geert van den Bogaart
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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20
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Abstract
Bacteria and archaea possess a protein complex in the plasma membrane that governs protein secretion and membrane protein insertion. Eukaryotes carry homologues in the endoplasmic reticulum (ER) where they direct the same reaction. A combination of experiments conducted on the systems found in all three domains of life has revealed a great deal about protein translocation. The channel provides a route for proteins to pass through the hydrophobic barrier of the membrane, assisted by various partner proteins which maintain an unfolded state of the substrate, target it to the channel and provide the energy and mechanical drive required for transport. In bacteria, the post-translational reaction utilizes an ATPase that couples the free energy of ATP binding and hydrolysis to move the substrate through the protein pore. This review will draw on genetic, biochemical and structural findings in an account of our current understanding of this mechanism.
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Affiliation(s)
- Vicki A M Gold
- Department of Biochemistry, University of Bristol, Bristol, UK
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21
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Cavanaugh LF, Palmer AG, Gierasch LM, Hunt JF. Disorder breathes life into a DEAD motor. Nat Struct Mol Biol 2006; 13:566-9. [PMID: 16826229 DOI: 10.1038/nsmb0706-566] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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van der Sluis EO, Nouwen N, Koch J, de Keyzer J, van der Does C, Tampé R, Driessen AJM. Identification of Two Interaction Sites in SecY that Are Important for the Functional Interaction with SecA. J Mol Biol 2006; 361:839-49. [PMID: 16890955 DOI: 10.1016/j.jmb.2006.07.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 07/03/2006] [Accepted: 07/12/2006] [Indexed: 11/24/2022]
Abstract
The motor protein SecA drives the translocation of (pre-)proteins across the SecYEG channel in the bacterial cytoplasmic membrane by nucleotide-dependent cycles of conformational changes often referred to as membrane insertion/de-insertion. Despite structural data on SecA and an archaeal homolog of SecYEG, the identity of the sites of interaction between SecA and SecYEG are unknown. Here, we show that SecA can be cross-linked to several residues in cytoplasmic loop 5 (C5) of SecY, and that SecA directly interacts with a part of transmembrane segment 4 (TMS4) of SecY that is buried in the membrane region of SecYEG. Mutagenesis of either the conserved Arg357 in C5 or Glu176 in TMS4 interferes with the catalytic activity of SecA but not with binding of SecA to SecYEG. Our data explain how conformational changes in SecA could be directly coupled to the previously proposed opening mechanism of the SecYEG channel.
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Affiliation(s)
- Eli O van der Sluis
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9751 NN Haren, The Netherlands
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23
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Musial-Siwek M, Rusch SL, Kendall DA. Probing the affinity of SecA for signal peptide in different environments. Biochemistry 2006; 44:13987-96. [PMID: 16229488 PMCID: PMC3094106 DOI: 10.1021/bi050882k] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
SecA, the peripheral subunit of the Escherichia coli preprotein translocase, interacts with a number of ligands during export, including signal peptides, membrane phospholipids, and nucleotides. Using fluorescence resonance energy transfer (FRET), we studied the interactions of wild-type (WT) and mutant SecAs with IAEDANS-labeled signal peptide, and how these interactions are modified in the presence of other transport ligands. We find that residues on the third alpha-helix in the preprotein cross-linking domain (PPXD) are important for the interaction of SecA and signal peptide. For SecA in aqueous solution, saturation binding data using FRET analysis fit a single-site binding model and yielded a Kd of 2.4 microM. FRET is inhibited for SecA in lipid vesicles relative to that in aqueous solution at a low signal peptide concentration. The sigmoidal nature of the binding curve suggests that SecA in lipids has two conformational states; our results do not support different oligomeric states of SecA. Using native gel electrophoresis, we establish signal peptide-induced SecA monomerization in both aqueous solution and lipid vesicles. Whereas the affinity of SecA for signal peptide in an aqueous environment is unaffected by temperature or the presence of nucleotides, in lipids the affinity decreases in the presence of ADP or AMP-PCP but increases at higher temperature. The latter finding is consistent with SecA existing in an elongated form while inserting the signal peptide into membranes.
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Affiliation(s)
| | | | - Debra A. Kendall
- To whom correspondence should be addressed: Department of Molecular and Cell Biology, 91 N. Eagleville Rd., University of Connecticut, Storrs, CT 06269-3125. Phone: (860) 486-1891. Fax: (860) 486-4331.
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24
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Papanikou E, Karamanou S, Baud C, Frank M, Sianidis G, Keramisanou D, Kalodimos CG, Kuhn A, Economou A. Identification of the Preprotein Binding Domain of SecA. J Biol Chem 2005; 280:43209-17. [PMID: 16243836 DOI: 10.1074/jbc.m509990200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SecA, the preprotein translocase ATPase, has a helicase DEAD motor. To catalyze protein translocation, SecA possesses two additional flexible domains absent from other helicases. Here we demonstrate that one of these "specificity domains" is a preprotein binding domain (PBD). PBD is essential for viability and protein translocation. PBD mutations do not abrogate the basal enzymatic properties of SecA (nucleotide binding and hydrolysis), nor do they prevent SecA binding to the SecYEG protein conducting channel. However, SecA PBD mutants fail to load preproteins onto SecYEG, and their translocation ATPase activity does not become stimulated by preproteins. Bulb and Stem, the two sterically proximal PBD substructures, are physically separable and have distinct roles. Stem binds signal peptides, whereas the Bulb binds mature preprotein regions as short as 25 amino acids. Binding of signal or mature region peptides or full-length preproteins causes distinct conformational changes to PBD and to the DEAD motor. We propose that (a) PBD is a preprotein receptor and a physical bridge connecting bound preproteins to the DEAD motor, and (b) preproteins control the ATPase cycle via PBD.
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Affiliation(s)
- Efrosyni Papanikou
- Institute of Molecular Biology and Biotechnology, F.O.R.T.H., University of Crete, P.O. Box 1527, GR-711 10 Iraklio, Crete, Greece
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25
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de Keyzer J, van der Sluis EO, Spelbrink REJ, Nijstad N, de Kruijff B, Nouwen N, van der Does C, Driessen AJM. Covalently dimerized SecA is functional in protein translocation. J Biol Chem 2005; 280:35255-60. [PMID: 16115882 DOI: 10.1074/jbc.m506157200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ATPase SecA provides the driving force for the transport of secretory proteins across the cytoplasmic membrane of Escherichia coli. SecA exists as a dimer in solution, but the exact oligomeric state of SecA during membrane binding and preprotein translocation is a topic of debate. To study the requirements of oligomeric changes in SecA during protein translocation, a non-dissociable SecA dimer was formed by oxidation of the carboxyl-terminal cysteines. The cross-linked SecA dimer interacts with the SecYEG complex with a similar stoichiometry as non-cross-linked SecA. Cross-linking reversibly disrupts the SecB binding site on SecA. However, in the absence of SecB, the activity of the disulfide-bonded SecA dimer is indistinguishable from wild-type SecA. Moreover, SecYEG binding stabilizes a cold sodium dodecylsulfate-resistant dimeric state of SecA. The results demonstrate that dissociation of the SecA dimer is not an essential feature of the protein translocation reaction.
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Affiliation(s)
- Jeanine de Keyzer
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Materials and Science Centre Plus, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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26
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Mergulhão FJM, Summers DK, Monteiro GA. Recombinant protein secretion in Escherichia coli. Biotechnol Adv 2005; 23:177-202. [PMID: 15763404 DOI: 10.1016/j.biotechadv.2004.11.003] [Citation(s) in RCA: 334] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Revised: 11/23/2004] [Accepted: 11/30/2004] [Indexed: 10/25/2022]
Abstract
The secretory production of recombinant proteins by the Gram-negative bacterium Escherichia coli has several advantages over intracellular production as inclusion bodies. In most cases, targeting protein to the periplasmic space or to the culture medium facilitates downstream processing, folding, and in vivo stability, enabling the production of soluble and biologically active proteins at a reduced process cost. This review presents several strategies that can be used for recombinant protein secretion in E. coli and discusses their advantages and limitations depending on the characteristics of the target protein to be produced.
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Affiliation(s)
- F J M Mergulhão
- Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Av. Rovisco Pais, Lisbon 1049-001, Portugal.
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27
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Natale P, den Blaauwen T, van der Does C, Driessen AJM. Conformational State of the SecYEG-Bound SecA Probed by Single Tryptophan Fluorescence Spectroscopy. Biochemistry 2005; 44:6424-32. [PMID: 15850376 DOI: 10.1021/bi047488r] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The SecYEG complex is a membrane-embedded channel that permits the passage of precursor proteins (preproteins) across the inner membrane of Escherichia coli. SecA is a molecular motor that associates with the SecYEG pore and drives the stepwise translocation of preproteins across the membrane through multiple cycles of ATP binding and hydrolysis. We have investigated the conformational state of soluble and SecYEG-bound SecA using single tryptophan mutants of SecA. The fluorescence spectral properties of the single tryptophans of SecA and their accessibility to the quencher acrylamide demonstrate that SecA undergoes a conformational change that results in a more compact structure upon binding of ATP and binding to the SecYEG pore. In addition, SecYEG-bound SecA undergoes ATP-dependent conformational changes that are not observed for soluble SecA. These data support a model in which binding to the SecYEG channel has a major impact on the SecA conformation.
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Affiliation(s)
- Paolo Natale
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9750 AA Haren, The Netherlands
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28
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Vrontou E, Economou A. Structure and function of SecA, the preprotein translocase nanomotor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:67-80. [PMID: 15546658 DOI: 10.1016/j.bbamcr.2004.06.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 06/03/2004] [Accepted: 06/17/2004] [Indexed: 11/22/2022]
Abstract
Most secretory proteins that are destined for the periplasm or the outer membrane are exported through the bacterial plasma membrane by the Sec translocase. Translocase is a complex nanomachine that moves processively along its aminoacyl polymeric substrates effectively pumping them to the periplasmic space. The salient features of this process are: (a) a membrane-embedded "clamp" formed by the trimeric SecYEG protein, (b) a "motor" provided by the dimeric SecA ATPase, (c) regulatory subunits that optimize catalysis and (d) both chemical and electrochemical metabolic energy. Significant recent strides have allowed structural, biochemical and biophysical dissection of the export reaction. A model incorporating stepwise strokes of the translocase nanomachine at work is discussed.
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Affiliation(s)
- Eleftheria Vrontou
- Laboratory Unicellular, Organisms Group, Institute of Molecular Biology and Biotechnology, FO.R.T.H. and Department of Biology, University of Crete, Vassilika Vouton, P.O. Box 1527, GR-711 10 Iraklio, Crete, Greece
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29
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van Roosmalen ML, Geukens N, Jongbloed JDH, Tjalsma H, Dubois JYF, Bron S, van Dijl JM, Anné J. Type I signal peptidases of Gram-positive bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:279-97. [PMID: 15546672 DOI: 10.1016/j.bbamcr.2004.05.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Accepted: 05/12/2004] [Indexed: 11/21/2022]
Abstract
Proteins that are exported from the cytoplasm to the periplasm and outer membrane of Gram-negative bacteria, or the cell wall and growth medium of Gram-positive bacteria, are generally synthesized as precursors with a cleavable signal peptide. During or shortly after pre-protein translocation across the cytoplasmic membrane, the signal peptide is removed by signal peptidases. Importantly, pre-protein processing by signal peptidases is essential for bacterial growth and viability. This review is focused on the signal peptidases of Gram-positive bacteria, Bacillus and Streptomyces species in particular. Evolutionary concepts, current knowledge of the catalytic mechanism, substrate specificity requirements and structural aspects are addressed. As major insights in signal peptidase function and structure have been obtained from studies on the signal peptidase LepB of Escherichia coli, similarities and differences between this enzyme and known Gram-positive signal peptidases are highlighted. Notably, while the incentive for previous research on Gram-positive signal peptidases was largely based on their role in the biotechnologically important process of protein secretion, present-day interest in these essential enzymes is primarily derived from the idea that they may serve as targets for novel anti-microbials.
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Affiliation(s)
- Maarten L van Roosmalen
- Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, Netherlands
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30
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Zito CR, Antony E, Hunt JF, Oliver DB, Hingorani MM. Role of a conserved glutamate residue in the Escherichia coli SecA ATPase mechanism. J Biol Chem 2005; 280:14611-9. [PMID: 15710614 PMCID: PMC4684309 DOI: 10.1074/jbc.m414224200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Escherichia coli SecA uses ATP to drive the transport of proteins across cell membranes. Glutamate 210 in the "DEVD" Walker B motif of the SecA ATP-binding site has been proposed as the catalytic base for ATP hydrolysis (Hunt, J. F., Weinkauf, S., Henry, L., Fak, J. J., McNicholas, P., Oliver, D. B., and Deisenhofer, J. (2002) Science 297, 2018-2026). Consistent with this hypothesis, we find that mutation of glutamate 210 to aspartate results in a 90-fold reduction of the ATP hydrolysis rate compared with wild type SecA, 0.3 s(-1) versus 27 s(-1), respectively. SecA-E210D also releases ADP at a slower rate compared with wild type SecA, suggesting that in addition to serving as the catalytic base, glutamate 210 might aid turnover as well. Our results contradict an earlier report that proposed aspartate 133 as the catalytic base (Sato, K., Mori, H., Yoshida, M., and Mizushima, S. (1996) J. Biol. Chem. 271, 17439-17444). Re-evaluation of the SecA-D133N mutant used in that study confirms its loss of ATPase and membrane translocation activities, but surprisingly, the analogous SecA-D133A mutant retains full activity, revealing that this residue does not play a key role in catalysis.
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Affiliation(s)
- Christopher R. Zito
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, Connecticut 06459
| | - Edwin Antony
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, Connecticut 06459
| | | | - Donald B. Oliver
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, Connecticut 06459
| | - Manju M. Hingorani
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, Connecticut 06459
- To whom correspondence should be addressed: Molecular Biology and Biochemistry Dept., Wesleyan University, 205 Hall-Atwater Laboratories, Middletown, CT 06459. Tel.: 860-685-2284; Fax: 860-685-2141;
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31
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Abstract
In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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32
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Wang L, Miller A, Rusch SL, Kendall DA. Demonstration of a specific Escherichia coli SecY-signal peptide interaction. Biochemistry 2004; 43:13185-92. [PMID: 15476412 PMCID: PMC3084660 DOI: 10.1021/bi049485k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein translocation in Escherichia coli is initiated by the interaction of a preprotein with the membrane translocase composed of a motor protein, SecA ATPase, and a membrane-embedded channel, the SecYEG complex. The extent to which the signal peptide region of the preprotein plays a role in SecYEG interactions is unclear, in part because studies in this area typically employ the entire preprotein. Using a synthetic signal peptide harboring a photoaffinity label in its hydrophobic core, we examined this interaction with SecYEG in a detergent micellar environment. The signal peptide was found to specifically bind SecY in a saturable manner and at levels comparable to those that stimulate SecA ATPase activity. Chemical and proteolytic cleavage of cross-linked SecY and analysis of the signal peptide adducts indicate that the binding was primarily to regions of the protein containing transmembrane domains seven and two. The signal peptide-SecY interaction was affected by the presence of SecA and nucleotides in a manner consistent with the transfer of signal peptide to SecY upon nucleotide hydrolysis at SecA.
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Affiliation(s)
| | | | | | - Debra A. Kendall
- To whom correspondence should be addressed: Department of Molecular and Cell Biology, 91 North Eagleville Road, The University of Connecticut, Storrs, CT 06269-3125. Tel: (860) 486-1891.
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33
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Veenendaal AKJ, van der Does C, Driessen AJM. The protein-conducting channel SecYEG. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2004; 1694:81-95. [PMID: 15546659 DOI: 10.1016/j.bbamcr.2004.02.009] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Revised: 01/30/2004] [Accepted: 02/02/2004] [Indexed: 10/26/2022]
Abstract
In bacteria, the translocase mediates the translocation of proteins into or across the cytosolic membrane. It consists of a membrane embedded protein-conducting channel and a peripherally associated motor domain, the ATPase SecA. The channel is formed by SecYEG, a multimeric protein complex that assembles into oligomeric forms. The structure and subunit composition of this protein-conducting channel is evolutionary conserved and a similar system is found in the endoplasmic reticulum of eukaryotes and the cytoplasmic membrane of archaea. The ribosome and other membrane proteins can associate with the protein-conducting channel complex and affect its activity or functionality.
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Affiliation(s)
- Andreas K J Veenendaal
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9750 AA Haren, The Netherlands
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34
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Fak JJ, Itkin A, Ciobanu DD, Lin EC, Song XJ, Chou YT, Gierasch LM, Hunt JF. Nucleotide exchange from the high-affinity ATP-binding site in SecA is the rate-limiting step in the ATPase cycle of the soluble enzyme and occurs through a specialized conformational state. Biochemistry 2004; 43:7307-27. [PMID: 15182175 DOI: 10.1021/bi0357208] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have characterized the kinetic and thermodynamic consequences of adenine nucleotide interaction with the low-affinity and high-affinity nucleotide-binding sites in free SecA. ATP binds to the hydrolytically active high-affinity site approximately 3-fold more slowly than ADP when SecA is in its conformational ground state, suggesting that ATP binding probably occurs when the enzyme is in another conformational state during the productive ATPase/transport cycle. The steady-state ATP hydrolysis rate is equivalent to the rate of ADP release from the high-affinity site under a number of conditions, indicating that this process is the rate-limiting step in the ATPase cycle of the free enzyme. Because efficient protein translocation requires at least a 100-fold acceleration in the ATPase rate, the rate-limiting process of ADP release from the high-affinity site is likely to play a controlling role in the conformational reaction cycle of SecA. This release process involves a large enthalpy of activation, suggesting that it involves a protein conformational change, and two observations indicate that this conformational change is different from the well-characterized endothermic conformational transition believed to gate the binding of SecA to SecYEG. First, nucleotide binding to the low-affinity site strongly inhibits the endothermic transition but does not reduce the rate of ADP release. Second, removal of Mg(2+) from an allosteric binding site on SecA does not perturb the endothermic transition but produces a 10-fold acceleration in the rate of ADP release. These divergent effects suggest that a specialized conformational transition mediates the rate-limiting ADP-release process in SecA. Finally, ADP, 2'-O-(N-methylanthraniloyl)-adenosine-5'-diphosphate (MANT-ADP), and adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma-S) bind with similar affinities to the high-affinity site and also to the low-affinity site as inferred from their consistent effects in inhibiting the endothermic transition. In contrast, adenosine 5'-(beta,gamma-imino)triphosphate (AMPPNP) shows 100-fold weaker affinity than ADP for the high-affinity site and no detectable interaction with the low-affinity site at concentrations up to 1 mM, suggesting that this nonhydrolyzable analogue may not be a faithful mimic of ATP in its interactions with SecA.
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Affiliation(s)
- John J Fak
- Department of Biological Sciences, 702A Fairchild Center, MC2434, Columbia University, New York, New York 10027, USA
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35
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Geukens N, Frederix F, Reekmans G, Lammertyn E, Van Mellaert L, Dehaen W, Maes G, Anné J. Analysis of type I signal peptidase affinity and specificity for preprotein substrates. Biochem Biophys Res Commun 2004; 314:459-67. [PMID: 14733928 DOI: 10.1016/j.bbrc.2003.12.122] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Type I signal peptidases (SPases) are membrane-bound endopeptidases responsible for the catalytic cleavage of signal peptides from secretory proteins. Here, we analysed the interaction between a bacterial type I SPase and preprotein substrates using surface plasmon resonance. The use of a home-made biosensor surface based on a mixed self-assembled monolayer of thiols on gold allowed qualitative and kinetic analysis. In vitro binding of purified preproteins to a covalently immobilised bacterial SPase was found to be rather efficient (apparent K(D)=10(-7)-10(-8)M). The signal peptide was shown to be a prerequisite for SPase binding and the nature of the mature part of the preprotein significantly affected SPase binding affinity. The developed biosensor containing immobilised SPase is of great importance for analysis of specificity at substrate binding level and for drug screening. In fact, this is the first report of a membrane protein that was covalently attached to a biosensor surface and that retained binding capacity.
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Affiliation(s)
- Nick Geukens
- Laboratory of Bacteriology, Rega Institute, K.U.Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium
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