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Baba K, Kamiya K. Molecular Transportation Conversion of Membrane Tension Using a Mechanosensitive Channel in Asymmetric Lipid-Protein Vesicles. ACS APPLIED MATERIALS & INTERFACES 2024; 16:21623-21632. [PMID: 38594642 DOI: 10.1021/acsami.4c02370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Giant lipid vesicles composed of a lipid bilayer form complex membrane structures and enzyme network reactions that can be used to construct well-defined artificial cell models based on microfluidic technologies and synthetic biology. As a different approach to cell-mimicking systems, we formed an asymmetric lipid-amphiphilic protein (oleosin) vesicle containing a lipid and an oleosin monolayer in the outer and inner leaflets, respectively. These asymmetric vesicles enabled the reconstitution and function of β-barrel types of membrane proteins (OmpG) and the fission of vesicles stimulated by lysophospholipids. These applications combine the advantages of the high stability of lipids and oleosin leaflets in asymmetric lipid-oleosin vesicles. In this study, to evaluate the versatility of this asymmetric lipid-oleosin vesicle, the molecular transport of the mechanosensitive channel of large conductance (MscL) with an α-helix was evaluated by changing the tension of the asymmetric vesicle membrane with lysophospholipid. A nanopore of MscL assembled as a pentamer of MscLs transports small molecules of less than 10 kDa by sensing physical stress at the lipid bilayer. The amount and maximum size of the small molecules transported via MscL in the asymmetric lipid-oleosin vesicles were compared to those in the lipid vesicles. We revealed the existence of the C- and N-terminal regions (cytoplasmic side) of MscL on the inner leaflet of the asymmetric lipid-oleosin vesicles using an insertion direction assay. Furthermore, the change in the tension of the lipid-oleosin membrane activated the proteins in these vesicles, inducing their transportation through MscL nanopores. Therefore, asymmetric lipid-oleosin vesicles containing MscL can be used as substrates to study the external environment response of complex artificial cell models.
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Affiliation(s)
- Kotaro Baba
- Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Koki Kamiya
- Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
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Bavi N, Martinac AD, Cortes DM, Bavi O, Ridone P, Nomura T, Hill AP, Martinac B, Perozo E. Structural Dynamics of the MscL C-terminal Domain. Sci Rep 2017; 7:17229. [PMID: 29222414 PMCID: PMC5722894 DOI: 10.1038/s41598-017-17396-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 11/16/2017] [Indexed: 12/17/2022] Open
Abstract
The large conductance mechanosensitive channel (MscL), acts as an osmoprotective emergency valve in bacteria by opening a large, water-filled pore in response to changes in membrane tension. In its closed configuration, the last 36 residues at the C-terminus form a bundle of five α-helices co-linear with the five-fold axis of symmetry. Here, we examined the structural dynamics of the C-terminus of EcMscL using site-directed spin labelling electron paramagnetic resonance (SDSL EPR) spectroscopy. These experiments were complemented with computational modelling including molecular dynamics (MD) simulations and finite element (FE) modelling. Our results show that under physiological conditions, the C-terminus is indeed an α-helical bundle, located near the five-fold symmetry axis of the molecule. Both experiments and computational modelling demonstrate that only the top part of the C-terminal domain (from the residue A110 to E118) dissociates during the channel gating, while the rest of the C-terminus stays assembled. This result is consistent with the view that the C-terminus functions as a molecular sieve and stabilizer of the oligomeric MscL structure as previously suggested.
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Affiliation(s)
- Navid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Adam D Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- School of Mechanical & Mining Engineering, University of Queensland, St. Lucia (Brisbane), QLD 4072, Brisbane, Australia
| | - D Marien Cortes
- Texas Tech University Health Sciences Center, Lubbock, Texas, 79430, USA
| | - Omid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Physics, University of Tehran, Tehran, 1439955961, Iran
| | - Pietro Ridone
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Takeshi Nomura
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Rehabilitation, Kyushu Nutrition Welfare University, Kitakyushu, 800-029, Japan
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia.
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia.
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 E 57th St, Chicago, Illinois, 60637, USA.
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Bavi N, Bavi O, Vossoughi M, Naghdabadi R, Hill AP, Martinac B, Jamali Y. Nanomechanical properties of MscL α helices: A steered molecular dynamics study. Channels (Austin) 2016; 11:209-223. [PMID: 27753526 DOI: 10.1080/19336950.2016.1249077] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Gating of mechanosensitive (MS) channels is driven by a hierarchical cascade of movements and deformations of transmembrane helices in response to bilayer tension. Determining the intrinsic mechanical properties of the individual transmembrane helices is therefore central to understanding the intricacies of the gating mechanism of MS channels. We used a constant-force steered molecular dynamics (SMD) approach to perform unidirectional pulling tests on all the helices of MscL in M. tuberculosis and E. coli homologs. Using this method, we could overcome the issues encountered with the commonly used constant-velocity SMD simulations, such as low mechanical stability of the helix during stretching and high dependency of the elastic properties on the pulling rate. We estimated Young's moduli of the α-helices of MscL to vary between 0.2 and 12.5 GPa with TM2 helix being the stiffest. We also studied the effect of water on the properties of the pore-lining TM1 helix. In the absence of water, this helix exhibited a much stiffer response. By monitoring the number of hydrogen bonds, it appears that water acts like a 'lubricant' (softener) during TM1 helix elongation. These data shed light on another physical aspect underlying hydrophobic gating of MS channels, in particular MscL.
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Affiliation(s)
- N Bavi
- a Division of Molecular Cardiology and Biophysics , Victor Chang Cardiac Research Institute , Darlinghurst , NSW , Australia.,b St Vincent's Clinical School, Faculty of Medicine , University of New South Wales , Darlinghurst , NSW , Australia
| | - O Bavi
- c Institute for Nanoscience and Nanotechnology, Sharif University of Technology , Tehran , Iran
| | - M Vossoughi
- c Institute for Nanoscience and Nanotechnology, Sharif University of Technology , Tehran , Iran.,d Biochemical & Bioenvironmental Research Center (BBRC) , Tehran , Iran
| | - R Naghdabadi
- c Institute for Nanoscience and Nanotechnology, Sharif University of Technology , Tehran , Iran.,e Department of Mechanical Engineering , Sharif University of Technology , Tehran , Iran
| | - A P Hill
- a Division of Molecular Cardiology and Biophysics , Victor Chang Cardiac Research Institute , Darlinghurst , NSW , Australia
| | - B Martinac
- a Division of Molecular Cardiology and Biophysics , Victor Chang Cardiac Research Institute , Darlinghurst , NSW , Australia.,b St Vincent's Clinical School, Faculty of Medicine , University of New South Wales , Darlinghurst , NSW , Australia
| | - Y Jamali
- f Department of Mathematics , Tarbiat Modares University , Tehran , Iran.,g Computational Physical Sciences Research Laboratory , School of Nanoscience, Institute for Research in Fundamental Sciences (IPM) , Tehran , Iran
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Chi G, Rohde PR, Ridone P, Hankamer B, Martinac B, Landsberg MJ. Functional similarities between heterogeneously and homogenously expressed MscL constructs. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:589-98. [PMID: 26233759 DOI: 10.1007/s00249-015-1062-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 06/29/2015] [Accepted: 07/14/2015] [Indexed: 11/30/2022]
Abstract
The mechanosensitive channel of large conductance MscL is a well-characterized mechanically gated non-selective ion channel, which often serves as a prototype mechanosensitive channel for mechanotransduction studies. However, there are some discrepancies between MscL constructs used in these studies, most notably unintended heterogeneous expression from some MscL expression constructs. In this study we investigate the possible cause of this expression pattern, and compare the original non-homogenously expressing constructs with our new homogeneously expressing one to confirm that there is little functional difference between them. In addition, a new MscL construct has been developed with an improved molar extinction coefficient at 280 nm, enabling more accurate protein quantification.
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Affiliation(s)
- Gamma Chi
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia
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Ando C, Liu N, Yoshimura K. A cytoplasmic helix is required for pentamer formation of the Escherichia coli MscL mechanosensitive channel. J Biochem 2015; 158:109-14. [PMID: 25697390 DOI: 10.1093/jb/mvv019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 01/14/2015] [Indexed: 01/01/2023] Open
Abstract
Many membrane proteins such as ion channels are oligomers, but the determinants of the degree of oligomerization are not fully understood. Mechanosensitive channel with large conductance (MscL), which is ubiquitous in bacteria, is a homopentamer with two transmembrane helices and a cytoplasmic helix in each subunit. The carboxyl-terminal cytoplasmic helices assemble into a pentameric bundle that resembles cartilage oligomeric matrix protein. To address the role of cytoplasmic helices in the pentamer formation of Escherichia coli MscL, we generated MscL constructs with various deletions at the carboxyl terminus and translated them in a cell-free system. Deletions of Leu-129 and the downstream sequence resulted in formation of various oligomers without preference to pentamers, suggesting that nearly the whole cytoplasmic helix is required for MscL pentamer formation.
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Affiliation(s)
- Chie Ando
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan
| | - Naili Liu
- Department of Biology, University of Maryland, 1210 Biology-Psychology Bldg., College Park, MD 20742, USA; and
| | - Kenjiro Yoshimura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan; Department of Biology, University of Maryland, 1210 Biology-Psychology Bldg., College Park, MD 20742, USA; and Department of Machinery and Control Systems, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama 337-8570, Japan
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Zhong D, Blount P. Electrostatics at the membrane define MscL channel mechanosensitivity and kinetics. FASEB J 2014; 28:5234-41. [PMID: 25223610 DOI: 10.1096/fj.14-259309] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The bacterial mechanosensitive channel of large conductance (MscL) serves as a biological emergency release valve, preventing the occurrence of cell lysis caused by acute osmotic stress. Its tractable nature allows it to serve as a paradigm for how a protein can directly sense membrane tension. Although much is known of the importance of the hydrophobicity of specific residues in channel gating, it has remained unclear whether electrostatics at the membrane plays any role. We studied MscL chimeras derived from functionally distinct orthologues: Escherichia coli and Staphylococcus aureus. Dissection of one set led to an observation that changing the charge of a single residue, K101, of E. coli (Ec)-MscL, effects a channel phenotype: when mutated to a negative residue, the channel is less mechanosensitive and has longer open dwell times. Assuming electrostatic interactions, we determined whether they are due to protein-protein or protein-lipid interactions by performing site-directed mutagenesis elsewhere in the protein and reconstituting channels into defined lipids, with and without negative head groups. We found that although both interactions appear to play some role, the primary determinant of the channel phenotype seems to be protein-lipid electrostatics. The data suggest a model for the role of electrostatic interactions in the dynamics of MscL gating.
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Affiliation(s)
- Dalian Zhong
- Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Cross M, Fernandes M, Dirr H, Fanucchi S. Glutamate 85 and glutamate 228 contribute to the pH-response of the soluble form of chloride intracellular channel 1. Mol Cell Biochem 2014; 398:83-93. [PMID: 25209805 DOI: 10.1007/s11010-014-2207-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 08/30/2014] [Indexed: 10/24/2022]
Abstract
The chloride intracellular channel protein, CLIC1, is synthesised as a soluble monomer that can reversibly bind membranes. Soluble CLIC1 is proposed to respond to the low pH found at a membrane surface by partially unfolding and restructuring into a membrane-competent conformation. This transition is proposed to be controlled by strategically located "pH-sensor" residues that become protonated at acidic pH. In this study, we investigate the role of two conserved glutamate residues, Glu85 in the N-domain and Glu228 in the C-domain, as pH-sensors. E85L and E228L CLIC1 variants were created to reduce pH sensitivity by permanently breaking the bonds these residues form. The structure and stability of each variant was compared to the wild type at both pH 7.0 and pH 5.5. Neither substitution significantly altered the structure but both decreased the conformational stability. Furthermore, E85L CLIC1 formed a urea-induced unfolding intermediate state at both pH 7 and pH 5.5 compared to wild-type and E228L CLIC1 which only formed the intermediate at pH 5.5. We conclude that Glu85 and Glu228 are two of the five pH-sensor residues of CLIC1 and contribute to the pH-response in different ways. Glu228 lowers the stability of the native state at pH 5.5, while Glu85 contributes both to the stability of the native state and to the formation of the intermediate state. By putting these interactions into the context of the three previously described CLIC1 pH-sensor residues, we propose a mechanism for the conversion of CLIC1 from the soluble state to the pre-membrane form.
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Affiliation(s)
- Megan Cross
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, 1 Jan Smuts Ave, Johannesburg, 2050, South Africa
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Martinac B, Nomura T, Chi G, Petrov E, Rohde PR, Battle AR, Foo A, Constantine M, Rothnagel R, Carne S, Deplazes E, Cornell B, Cranfield CG, Hankamer B, Landsberg MJ. Bacterial mechanosensitive channels: models for studying mechanosensory transduction. Antioxid Redox Signal 2014; 20:952-69. [PMID: 23834368 DOI: 10.1089/ars.2013.5471] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SIGNIFICANCE Sensations of touch and hearing are manifestations of mechanical contact and air pressure acting on touch receptors and hair cells of the inner ear, respectively. In bacteria, osmotic pressure exerts a significant mechanical force on their cellular membrane. Bacteria have evolved mechanosensitive (MS) channels to cope with excessive turgor pressure resulting from a hypo-osmotic shock. MS channel opening allows the expulsion of osmolytes and water, thereby restoring normal cellular turgor and preventing cell lysis. RECENT ADVANCES As biological force-sensing systems, MS channels have been identified as the best examples of membrane proteins coupling molecular dynamics to cellular mechanics. The bacterial MS channel of large conductance (MscL) and MS channel of small conductance (MscS) have been subjected to extensive biophysical, biochemical, genetic, and structural analyses. These studies have established MscL and MscS as model systems for mechanosensory transduction. CRITICAL ISSUES In recent years, MS ion channels in mammalian cells have moved into focus of mechanotransduction research, accompanied by an increased awareness of the role they may play in the pathophysiology of diseases, including cardiac hypertrophy, muscular dystrophy, or Xerocytosis. FUTURE DIRECTIONS A recent exciting development includes the molecular identification of Piezo proteins, which function as nonselective cation channels in mechanosensory transduction associated with senses of touch and pain. Since research on Piezo channels is very young, applying lessons learned from studies of bacterial MS channels to establishing the mechanism by which the Piezo channels are mechanically activated remains one of the future challenges toward a better understanding of the role that MS channels play in mechanobiology.
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Affiliation(s)
- Boris Martinac
- 1 Molecular Cardiology and Biophysics Division/Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute , Darlinghurst, Australia
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A lipid-mediated conformational switch modulates the thermosensing activity of DesK. Proc Natl Acad Sci U S A 2014; 111:3579-84. [PMID: 24522108 DOI: 10.1073/pnas.1317147111] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The thermosensor DesK is a multipass transmembrane histidine-kinase that allows the bacterium Bacillus subtilis to adjust the levels of unsaturated fatty acids required to optimize membrane lipid fluidity. The cytoplasmic catalytic domain of DesK behaves like a kinase at low temperature and like a phosphatase at high temperature. Temperature sensing involves a built-in instability caused by a group of hydrophilic residues located near the N terminus of the first transmembrane (TM) segment. These residues are buried in the lipid phase at low temperature and partially "buoy" to the aqueous phase at higher temperature with the thinning of the membrane, promoting the required conformational change. Nevertheless, the core question remains poorly understood: How is the information sensed by the transmembrane region converted into a rearrangement in the cytoplasmic catalytic domain to control DesK activity? Here, we identify a "linker region" (KSRKERERLEEK) that connects the TM sensor domain with the cytoplasmic catalytic domain involved in signal transmission. The linker adopts two conformational states in response to temperature-dependent membrane thickness changes: (i) random coiled and bound to the phospholipid head groups at the water-membrane interface, promoting the phosphatase state or (ii) unbound and forming a continuous helix spanning a region from the membrane to the cytoplasm, promoting the kinase state. Our results uphold the view that the linker is endowed with a helix/random coil conformational duality that enables it to behave like a transmission switch, with helix disruption decreasing the kinase/phosphatase activity ratio, as required to modulate the DesK output response.
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Iscla I, Blount P. Sensing and responding to membrane tension: the bacterial MscL channel as a model system. Biophys J 2012; 103:169-74. [PMID: 22853893 DOI: 10.1016/j.bpj.2012.06.021] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/11/2012] [Accepted: 06/12/2012] [Indexed: 12/21/2022] Open
Abstract
Mechanosensors are important for many life functions, including the senses of touch, balance, and proprioception; cardiovascular regulation; kidney function; and osmoregulation. Many channels from an assortment of families are now candidates for eukaryotic mechanosensors and proprioception, as well as cardiovascular regulation, kidney function, and osmoregulation. Bacteria also possess two families of mechanosensitive channels, termed MscL and MscS, that function as osmotic emergency release valves. Of the two channels, MscL is the most conserved, most streamlined in structure, and largest in conductance at 3.6 nS with a pore diameter in excess of 30 Å; hence, the structural changes required for gating are exaggerated and perhaps more easily defined. Because of these properties, as well as its tractable nature, MscL represents a excellent model for studying how a channel can sense and respond to biophysical changes of a lipid bilayer. Many of the properties of the MscL channel, such as the sensitivity to amphipaths, a helix that runs along the membrane surface and is connected to the pore via a glycine, a twisting and turning of the transmembrane domains upon gating, and the dynamic changes in membrane interactions, may be common to other candidate mechanosensors. Here we review many of these properties and discuss their structural and functional implications.
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Affiliation(s)
- Irene Iscla
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, Texas. USA
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Bonardi F, Nouwen N, Feringa BL, Driessen AJM. Protein conducting channels—mechanisms, structures and applications. MOLECULAR BIOSYSTEMS 2012; 8:709-19. [DOI: 10.1039/c2mb05433g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Iscla I, Wray R, Blount P. An in vivo screen reveals protein-lipid interactions crucial for gating a mechanosensitive channel. FASEB J 2011; 25:694-702. [PMID: 21068398 PMCID: PMC3023395 DOI: 10.1096/fj.10-170878] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2010] [Accepted: 10/28/2010] [Indexed: 11/11/2022]
Abstract
The bacterial mechanosensitive channel MscL is the best-studied mechanosensor, thus serving as a paradigm of how a protein senses and responds to mechanical force. Models for the transition of Escherichia coli MscL from closed to open states propose a tilting of the transmembrane domains in the plane of the membrane, suggesting dynamic protein-lipid interactions. Here, we used a rapid in vivo assay to assess the function of channels that were post-translationally modified at several different sites in a region just distal to the cytoplasmic end of the second transmembrane helix. We utilized multiple probes with various affinities for the membrane environment. The in vivo functional data, combined with site-directed mutagenesis, single-channel analyses, and tryptophan fluorescence measurements, confirmed that lipid interactions within this region are critical for MscL gating. The data suggest a model in which this region acts as an anchor for the transmembrane domain tilting during gating. Furthermore, the conservation of analogous motifs among many other channels suggests a conserved protein-lipid dynamic mechanism.
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Affiliation(s)
- Irene Iscla
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
| | - Robin Wray
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
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Abstract
Bacterial ion channels were known, but only in special cases, such as outer membrane porins in Escherichia coli and bacterial toxins that form pores in their target (bacterial or mammalian) membranes. The exhaustive coverage provided by a decade of bacterial genome sequencing has revealed that ion channels are actually widespread in bacteria, with homologs of a broad range of mammalian channel proteins coded throughout the bacterial and archaeal kingdoms. This review discusses four groups of bacterial channels: porins, mechano-sensitive (MS) channels, channel-forming toxins, and bacterial homologs of mammalian channels. The outer membrane (OM) of gram-negative bacteria blocks access of essential nutrients; to survive, the cell needs to provide a mechanism for nutrients to penetrate the OM. Porin channels provide this access by forming large, nonspecific aqueous pores in the OM that allow ions and vital nutrients to cross it and enter the periplasm. MS channels act as emergency release valves, allowing solutes to rapidly exit the cytoplasm and to dissipate the large osmotic disparity between the internal and external environments. MS channels are remarkable in that they do this by responding to forces exerted by the membrane itself. Some bacteria produce toxic proteins that form pores in trans, attacking and killing other organisms by virtue of their pore formation. The review focuses on those bacterial toxins that kill other bacteria, specifically the class of proteins called colicins. Colicins reveal the dangers of channel formation in the plasma membrane, since they kill their targets with exactly that approach.
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Bringing ion channel crystal structures into sharper focus with computer modeling: examples from mechanosensitive channels. Future Med Chem 2010; 2:909-13. [DOI: 10.4155/fmc.10.28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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15
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Yoshimura K, Sokabe M. Mechanosensitivity of ion channels based on protein-lipid interactions. J R Soc Interface 2010. [PMID: 20356872 DOI: 10.1098/rsif.2010.0095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Ion channels form a group of membrane proteins that pass ions through a pore beyond the energy barrier of the lipid bilayer. The structure of the transmembrane segment of membrane proteins is influenced by the charges and the hydrophobicity of the surrounding lipids and the pressure on its surface. A mechanosensitive channel is specifically designed to change its conformation in response to changes in the membrane pressure (tension). However, mechanosensitive channels are not the only group that is sensitive to the physical environment of the membrane: voltage-gated channels are also amenable to the lipid environment. In this article, we review the structure and gating mechanisms of the mechanosensitive channels and voltage-gated channels and discuss how their functions are affected by the physical properties of the lipid bilayer.
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Affiliation(s)
- Kenjiro Yoshimura
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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Yoshimura K, Sokabe M. Mechanosensitivity of ion channels based on protein-lipid interactions. J R Soc Interface 2010; 7 Suppl 3:S307-20. [PMID: 20356872 DOI: 10.1098/rsif.2010.0095.focus] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ion channels form a group of membrane proteins that pass ions through a pore beyond the energy barrier of the lipid bilayer. The structure of the transmembrane segment of membrane proteins is influenced by the charges and the hydrophobicity of the surrounding lipids and the pressure on its surface. A mechanosensitive channel is specifically designed to change its conformation in response to changes in the membrane pressure (tension). However, mechanosensitive channels are not the only group that is sensitive to the physical environment of the membrane: voltage-gated channels are also amenable to the lipid environment. In this article, we review the structure and gating mechanisms of the mechanosensitive channels and voltage-gated channels and discuss how their functions are affected by the physical properties of the lipid bilayer.
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Affiliation(s)
- Kenjiro Yoshimura
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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Cloning and functional expression of an MscL ortholog from Rhizobium etli: characterization of a mechanosensitive channel. J Membr Biol 2010; 234:13-27. [PMID: 20177670 DOI: 10.1007/s00232-010-9235-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 01/26/2010] [Indexed: 10/19/2022]
Abstract
Rhizobium etli is equipped with several systems to handle both hyper- and hypo-osmotic stress. For adaptation to hypo-osmotic stress, R. etli possesses a single gene with clear homology to MscS, four MscS-like channels and one ortholog of MscL (ReMscL, identity approximately 44% compared to Escherichia coli MscL). We subcloned and expressed the ReMscL channel ortholog from R. etli in E. coli to examine its activity by patch clamp in giant spheroplasts and characterized it at the single-channel level. We obtained evidence that ReMscL prevents the lysis of E. coli null mutant log-phase cells upon a rapid, osmotic downshock and identified a slight pH dependence for ReMscL activation. Here, we describe the facilitation of ReMscL activation by arachidonic acid (AA) and a reversible inhibitory effect of Gd(3+). The results obtained in these experiments suggest a stabilizing effect of micromolar AA and traces of Gd(3+) ions in the partially expanded conformation of the protein. Finally, we discuss a possible correlation between the number of gene paralogs for MS channels and the habitats of several microorganisms. Taken together, our data show that ReMscL may play an important role in free-living rhizobacteria during hypo-osmotic shock in the rhizosphere.
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Tan K, Sather A, Robertson JL, Moy S, Roux B, Joachimiak A. Structure and electrostatic property of cytoplasmic domain of ZntB transporter. Protein Sci 2009; 18:2043-52. [PMID: 19653298 DOI: 10.1002/pro.215] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ZntB is the distant homolog of CorA Mg(2+) transporter within the metal ion transporter superfamily. It was early reported that the ZntB from Salmonella typhimurium facilitated efflux of Zn(2+) and Cd(2+), but not Mg(2+). Here, we report the 1.90 A crystal structure of the intracellular domain of ZntB from Vibrio parahemolyticus. The domain forms a funnel-shaped homopentamer that is similar to the full-length CorA from Thermatoga maritima, but differs from two previously reported dimeric structures of truncated CorA intracellular domains. However, no Zn(2+) or Cd(2+) binding sites were identified in the high-resolution structure. Instead, 25 well-defined Cl(-) ions were observed and some of these binding sites are highly conserved within the ZntB family. Continuum electrostatics calculations suggest that the central pore of the funnel is highly attractive for cations, especially divalents. The presence of the bound Cl(-) ions increases the stability of cations along the pore suggesting they could be important in enhancing cation transport.
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Affiliation(s)
- Kemin Tan
- Midwest Center for Structural Genomics and Structural Biology Center, Argonne, Illinois 60439, USA
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19
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Bax Inhibitor-1, a conserved cell death suppressor, is a key molecular switch downstream from a variety of biotic and abiotic stress signals in plants. Int J Mol Sci 2009; 10:3149-3167. [PMID: 19742129 PMCID: PMC2738916 DOI: 10.3390/ijms10073149] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/06/2009] [Accepted: 07/06/2009] [Indexed: 02/03/2023] Open
Abstract
In Nature plants are constantly challenged by a variety of environmental stresses that could lead to disruptions in cellular homeostasis. Programmed cell death (PCD) is a fundamental cellular process that is often associated with defense responses to pathogens, during development and in response to abiotic stresses in fungi, animals and plants. Although there are many characteristics shared between different types of PCD events, it remains unknown whether a common mechanism drives various types of PCD in eukaryotes. One candidate regulator for such a mechanism is Bax Inhibitor-1 (BI-1), an evolutionary conserved, endoplasmic reticulum (ER)-resident protein that represents an ancient cell death regulator that potentially regulates PCD in all eukaryotes. Recent findings strongly suggested that BI-1 plays an important role in the conserved ER stress response pathway to modulate cell death induction in response to multiple types of cell death signals. As ER stress signaling pathways has been suggested to play important roles not only in the control of ER homeostasis but also in other biological processes such as the response to pathogens and abiotic stress in plants, BI-1 might function to control the convergence point that modulates the level of the “pro-survival and pro-death” signals under multiple stress conditions.
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20
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Balleza D, Gómez-Lagunas F. Conserved motifs in mechanosensitive channels MscL and MscS. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:1013-27. [PMID: 19424690 DOI: 10.1007/s00249-009-0460-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 03/27/2009] [Accepted: 04/08/2009] [Indexed: 11/29/2022]
Abstract
Mechanosensitive (MS) channels play a major role in protecting bacterial cells against hypo-osmotic shock. To understand their function, it is important to identify the conserved motifs using sequence analysis methods. In this study, the sequence conservation was investigated by an in silico analysis to generate sequence logos. We have identified new conserved motifs in the domains TM1, TM2 and the cytoplasmic helix from 231 homologs of MS channel of large conductance (MscL). In addition, we have identified new motifs for the TM3 and the cytoplasmic carboxy-terminal domain from 309 homologs of MS channel of small conductance (MscS). We found that the conservation in MscL homologs is high for TM1 and TM2 in the three domains of life. The conservation in MscS homologs is high only for TM3 in Bacteria and Archaea.
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Affiliation(s)
- Daniel Balleza
- Laboratory of Molecular Biology, University of Wisconsin, 1525 Linden Drive, Madison, WI, 53706, USA.
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21
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Ahn T, Yun CH, Chae HZ, Kim HR, Chae HJ. Ca2+/H+antiporter-like activity of human recombinant Bax inhibitor-1 reconstituted into liposomes. FEBS J 2009; 276:2285-91. [DOI: 10.1111/j.1742-4658.2009.06956.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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22
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Powl AM, East JM, Lee AG. Importance of Direct Interactions with Lipids for the Function of the Mechanosensitive Channel MscL. Biochemistry 2008; 47:12175-84. [DOI: 10.1021/bi801352a] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew M. Powl
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
| | - J. Malcolm East
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
| | - Anthony G. Lee
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
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23
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Abstract
Studies of ion channels have for long been dominated by the animalcentric, if not anthropocentric, view of physiology. The structures and activities of ion channels had, however, evolved long before the appearance of complex multicellular organisms on earth. The diversity of ion channels existing in cellular membranes of prokaryotes is a good example. Although at first it may appear as a paradox that most of what we know about the structure of eukaryotic ion channels is based on the structure of bacterial channels, this should not be surprising given the evolutionary relatedness of all living organisms and suitability of microbial cells for structural studies of biological macromolecules in a laboratory environment. Genome sequences of the human as well as various microbial, plant, and animal organisms unambiguously established the evolutionary links, whereas crystallographic studies of the structures of major types of ion channels published over the last decade clearly demonstrated the advantage of using microbes as experimental organisms. The purpose of this review is not only to provide an account of acquired knowledge on microbial ion channels but also to show that the study of microbes and their ion channels may also hold a key to solving unresolved molecular mysteries in the future.
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Affiliation(s)
- Boris Martinac
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia.
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24
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Tang Y, Yoo J, Yethiraj A, Cui Q, Chen X. Mechanosensitive channels: insights from continuum-based simulations. Cell Biochem Biophys 2008; 52:1-18. [PMID: 18787764 PMCID: PMC2651832 DOI: 10.1007/s12013-008-9024-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2008] [Indexed: 11/25/2022]
Abstract
Mechanotransduction plays an important role in regulating cell functions and it is an active topic of research in biophysics. Despite recent advances in experimental and numerical techniques, the intrinsic multiscale nature imposes tremendous challenges for revealing the working mechanisms of mechanosensitive channels. Recently, a continuum-mechanics-based hierarchical modeling and simulation framework has been established and applied to study the mechanical responses and gating behaviors of a prototypical mechanosensitive channel, the mechanosensitive channel of large conductance (MscL) in bacteria Escherichia coli (E. coli), from which several putative gating mechanisms have been tested and new insights are deduced. This article reviews these latest findings using the continuum mechanics framework and suggests possible improvements for future simulation studies. This computationally efficient and versatile continuum-mechanics-based protocol is poised to make contributions to the study of a variety of mechanobiology problems.
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Affiliation(s)
- Yuye Tang
- Nanomechanics Research Center, Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
| | - Jejoong Yoo
- Theoretical Chemistry Institute, Department of Chemistry, University of Wisconsin, Madison, WI 53706
| | - Arun Yethiraj
- Theoretical Chemistry Institute, Department of Chemistry, University of Wisconsin, Madison, WI 53706
| | - Qiang Cui
- Theoretical Chemistry Institute, Department of Chemistry, University of Wisconsin, Madison, WI 53706
| | - Xi Chen
- Nanomechanics Research Center, Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
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25
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Corry B, Martinac B. Bacterial mechanosensitive channels: Experiment and theory. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1859-70. [PMID: 17662237 DOI: 10.1016/j.bbamem.2007.06.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 06/25/2007] [Accepted: 06/26/2007] [Indexed: 11/24/2022]
Abstract
Since their discovery in Escherichia coli some 20 years ago, studies of bacterial mechanosensitive (MS) ion channels have been at the forefront of the MS channel research field. Two major events greatly advanced the research on bacterial MS channels: (i) cloning of MscL and MscS, the MS channels of Large and Small conductance, and (ii) solving their 3D crystal structure. These events enabled further experimental studies employing EPR and FRET spectroscopy in addition to patch clamp and molecular biological techniques that have successfully been used in characterization of the structure and function of bacterial MS channels. In parallel with the experimental studies computational modelling has been applied to elucidate the molecular dynamics of MscL and MscS, which has significantly contributed to our understanding of basic physical principles of the mechanosensory transduction in living organisms.
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Affiliation(s)
- Ben Corry
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6008, Australia
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26
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Kim HR, Lee GH, Ha KC, Ahn T, Moon JY, Lee BJ, Cho SG, Kim S, Seo YR, Shin YJ, Chae SW, Reed JC, Chae HJ. Bax Inhibitor-1 Is a pH-dependent regulator of Ca2+ channel activity in the endoplasmic reticulum. J Biol Chem 2008; 283:15946-55. [PMID: 18378668 DOI: 10.1074/jbc.m800075200] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In this study, Bax inhibitor-1 (BI-1) overexpression reduces the ER pool of Ca(2+) released by thapsigargin. Cells overexpressing BI-1 also showed lower intracellular Ca(2+) release induced by the Ca(2+) ionophore ionomycin as well as agonists of ryanodine receptors and inositol trisphosphate receptors. In contrast, cells expressing carboxyl-terminal deleted BI-1 (CDelta-BI-1 cells) displayed normal intracellular Ca(2+) mobilization. Basal Ca(2+) release rates from the ER were higher in BI-1-overexpressing cells than in control or CDelta-BI-1 cells. We determined that the carboxyl-terminal cytosolic region of BI-1 contains a lysine-rich motif (EKDKKKEKK) resembling the pH-sensing domains of ion channels. Acidic conditions triggered more extensive Ca(2+) release from ER microsomes from BI-1-overexpressing cells and BI-1-reconstituted liposomes. Acidic conditions also induced BI-1 protein oligomerization. Interestingly subjecting BI-1-overexpressing cells to acidic conditions induced more Bax recruitment to mitochondria, more cytochrome c release from mitochondria, and more cell death. These findings suggest that BI-1 increases Ca(2+) leak rates from the ER through a mechanism that is dependent on pH and on the carboxyl-terminal cytosolic region of the BI-1 protein. The findings also reveal a cell death-promoting phenotype for BI-1 that is manifested under low pH conditions.
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Affiliation(s)
- Hyung-Ryong Kim
- Department of Dental Pharmacology and Wonkwang Biomaterial Implant Research Institute, School of Dentistry, Wonkwang University, Iksan, Chonbuk 570-749, Republic of Korea
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27
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Abstract
The structure of the C-terminal domain of the mechanosensitive channel of large conductance (MscL) has generated significant controversy. As a result, several structures have been proposed for this region: the original crystal structure (1MSL) of the Mycobacterium tuberculosis homolog (Tb), a model of the Escherichia coli homolog, and, most recently, a revised crystal structure of Tb-MscL (2OAR). To understand which of these structures represents a physiological conformation, we measured the impact of mutations to the C-terminal domain on the thermal stability of Tb-MscL using circular dichroism and performed molecular dynamics simulations of the original and the revised crystal structures of Tb-MscL. Our results imply that this region is helical and adopts an alpha-helical bundle conformation similar to that observed in the E. coli MscL model and the revised Tb-MscL crystal structure.
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28
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Kloda A, Petrov E, Meyer GR, Nguyen T, Hurst AC, Hool L, Martinac B. Mechanosensitive channel of large conductance. Int J Biochem Cell Biol 2008; 40:164-9. [PMID: 17350877 DOI: 10.1016/j.biocel.2007.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 01/23/2007] [Accepted: 02/01/2007] [Indexed: 11/18/2022]
Abstract
Microbial cells constitutively express the Large Conductance Mechanosensitive Channel which opens in response to stretch forces in the lipid bilayer. The channel protein forms a homopentamer with each subunit containing two transmembrane regions and gates via the bilayer mechanism evoked by hydrophobic mismatch and changes in the membrane curvature and/or transbilayer pressure profile. During the stationary phase and during osmotic shock the channel protein is up-regulated to prevent cell lysis. Pharmacological potential of MscL may involve discovery of new age antibiotics to combat multiple drug-resistant bacterial strains.
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Affiliation(s)
- Anna Kloda
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
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29
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Debret G, Valadié H, Stadler AM, Etchebest C. New insights of membrane environment effects on MscL channel mechanics from theoretical approaches. Proteins 2007; 71:1183-96. [DOI: 10.1002/prot.21810] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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30
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Abstract
Two-pore-domain K(+) (K(2P)) channel subunits are made up of four transmembrane segments and two pore-forming domains that are arranged in tandem and function as either homo- or heterodimeric channels. This structural motif is associated with unusual gating properties, including background channel activity and sensitivity to membrane stretch. Moreover, K(2P) channels are modulated by a variety of cellular lipids and pharmacological agents, including polyunsaturated fatty acids and volatile general anaesthetics. Recent in vivo studies have demonstrated that TREK1, the most thoroughly studied K(2P) channel, has a key role in the cellular mechanisms of neuroprotection, anaesthesia, pain and depression.
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Affiliation(s)
- Eric Honoré
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR 6097, Université de Nice-Sophia Antipolis, 660 route des Lucioles, 06560 Valbonne, France.
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31
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Nakayama Y, Fujiu K, Sokabe M, Yoshimura K. Molecular and electrophysiological characterization of a mechanosensitive channel expressed in the chloroplasts of Chlamydomonas. Proc Natl Acad Sci U S A 2007; 104:5883-8. [PMID: 17389370 PMCID: PMC1851586 DOI: 10.1073/pnas.0609996104] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
MscS is a mechanosensitive channel that is ubiquitous among bacteria. Recent progress in the genome projects has revealed that homologs of MscS are also present in eukaryotes, but whether they operate as ion channels is unknown. In this study we cloned MSC1, a homolog of MscS in Chlamydomonas, and examined its function when expressed in Escherichia coli. Full-length MSC1 was not functional when expressed in E. coli cells. However, removal of the N-terminal signal sequence (DeltaN-MSC1) reversed this effect. DeltaN-MSC1 was found to open in response to membrane stretch and displayed a preference for anions over cations as permeable ions. DeltaN-MSC1 exhibited marked hysteretic behavior in response to ascending and descending stimuli. That is, channel gating occurred in response to significant stimuli but remained open until the stimulus was almost completely removed. Indirect immunofluorescence revealed that MSC1 is present as punctate spots in the cytoplasm and chloroplasts. Moreover, knockdown of MSC1 expression resulted in the abnormal localization of chlorophyll. These findings show that MSC1 is an intracellular mechanosensitive channel and is responsible for the organization of chloroplast in Chlamydomonas.
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Affiliation(s)
- Yoshitaka Nakayama
- *Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan
| | - Kenta Fujiu
- ICORP/SORST Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Nagoya 466-8550, Japan
| | - Masahiro Sokabe
- ICORP/SORST Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Nagoya 466-8550, Japan
- Department of Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; and
| | - Kenjiro Yoshimura
- *Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan
- ICORP/SORST Cell Mechanosensing Project, Japan Science and Technology Agency, 65 Tsurumai, Nagoya 466-8550, Japan
- Department of Bioenvironmental Science, Okazaki Institute for Integrative Biosciences, Okazaki, Aichi 444-8787, Japan
- To whom correspondence should be addressed. E-mail:
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32
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Zonia L, Munnik T. Life under pressure: hydrostatic pressure in cell growth and function. TRENDS IN PLANT SCIENCE 2007; 12:90-7. [PMID: 17293155 DOI: 10.1016/j.tplants.2007.01.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 01/02/2007] [Accepted: 01/31/2007] [Indexed: 05/08/2023]
Abstract
H(2)O is one of the most essential molecules for cellular life. Cell volume, osmolality and hydrostatic pressure are tightly controlled by multiple signaling cascades and they drive crucial cellular functions ranging from exocytosis and growth to apoptosis. Ion fluxes and cell shape restructuring induce asymmetries in osmotic potential across the plasma membrane and lead to localized hydrodynamic flow. Cells have evolved fascinating strategies to harness the potential of hydrodynamic flow to perform crucial functions. Plants exploit hydrodynamics to drive processes including gas exchange, leaf positioning, nutrient acquisition and growth. This paradigm is extended by recent work that reveals an important role for hydrodynamics in pollen tube growth.
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Affiliation(s)
- Laura Zonia
- Department of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, Netherlands.
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33
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The MscS Cytoplasmic Domain and Its Conformational Changes on the Channel Gating. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58011-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Lipid Effects on Mechanosensitive Channels. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58006-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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35
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MscL: The Bacterial Mechanosensitive Channel of Large Conductance. MECHANOSENSITIVE ION CHANNELS, PART A 2007. [DOI: 10.1016/s1063-5823(06)58008-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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36
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3.5 Billion Years of Mechanosensory Transduction: Structure and Function of Mechanosensitive Channels in Prokaryotes. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58002-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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37
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Payandeh J, Pai EF. A structural basis for Mg2+ homeostasis and the CorA translocation cycle. EMBO J 2006; 25:3762-73. [PMID: 16902408 PMCID: PMC1553185 DOI: 10.1038/sj.emboj.7601269] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 07/13/2006] [Indexed: 01/07/2023] Open
Abstract
We describe the CorA Mg(2+) transporter homologue from Thermotoga maritima in complex with 12 divalent cations at 3.7 A resolution. One metal is found near the universally conserved GMN motif, apparently stabilized within the transmembrane region. This portion of the selectivity filter might discriminate between the size and preferred coordination geometry of hydrated substrates. CorA may further achieve specificity by requiring the sequential dehydration of substrates along the length of its approximately 55 A long pore. Ten metal sites identified within the cytoplasmic funnel domain are linked to long extensions of the pore helices and regulate the transport status of CorA. We have characterized this region as an intrinsic divalent cation sensor and provide evidence that it functions as a Mg(2+)-specific homeostatic molecular switch. A proteolytic protection assay, biophysical data, and comparison to a soluble domain structure from Archaeoglobus fulgidus have revealed the potential reaction coordinate for this diverse family of transport proteins.
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Affiliation(s)
- Jian Payandeh
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, 101 College Street, Toronto, Ontario, Canada M5G 1L7. Tel.: 416 581 7545; Fax: 416 581 7545; E-mail: or
| | - Emil F Pai
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular & Medical Genetics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, 101 College Street, Toronto, Ontario, Canada M5G 1L7. Tel.: 416 581 7545; Fax: 416 581 7545; E-mail: or
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