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Ma S, Zhang Y, Zhang X, Xie H, Tong Q, Yu K, Yang J. Dynamic Interactions Between Brilliant Green and MscL Investigated by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations. Chemistry 2023; 29:e202202106. [PMID: 36251739 DOI: 10.1002/chem.202202106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Indexed: 11/22/2022]
Abstract
The mechanosensitive ion channel of large conductance (MscL) is a promising template for the development of new antibiotics due to its high conservation and uniqueness to microbes. Brilliant green (BG), a triarylmethane dye, has been identified as a new antibiotic targeted MscL. However, the detailed binding sites to MscL and the dynamic pathway of BG through the MscL channel remain unknown. Here, the dynamic interactions between BG and MscL were investigated using solid-state NMR spectroscopy and molecule dynamics (MD) simulations. Residue site-specific binding sites of BG to the MscL channel were identified by solid-state NMR. In addition, MD simulations revealed that BG conducts through the MscL channel via residues along the inner surface of the pore sequentially, in which the strong hydrophobic interactions between BG and hydrophobic residues F23 and I27 in the hydrophobic gate region of the MscL channel are major restrictions. Particularly, it was demonstrated that BG activates the MscL channel by reducing the hydrophobicity of the F23 in the gate region by water molecules that are bound to BG. Taken together, these simulations and experimental data provide novel insights into the dynamic interactions between BG and MscL, based on which new hydrophobic antibiotics and adjuvants targeting MscL can be developed.
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Affiliation(s)
- Shaojie Ma
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, P.R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China
| | - Yan Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Xuning Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China
| | - Huayong Xie
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
| | - Qiong Tong
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
| | - Kunqian Yu
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, P.R. China
| | - Jun Yang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China.,Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.,University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
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2
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Mechanosensitive channel Piezo1 induces cell apoptosis in pancreatic cancer by ultrasound with microbubbles. iScience 2022; 25:103733. [PMID: 35118354 PMCID: PMC8792083 DOI: 10.1016/j.isci.2022.103733] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 11/23/2021] [Accepted: 01/03/2022] [Indexed: 12/27/2022] Open
Abstract
Ultrasound (US), as a safe and non-invasive tool, has drawn researchers' attention to treat pancreatic ductal adenocarcinoma (PDAC). Piezo1, a mechanosensitive channel, can be activated by various mechanical stimuli. In this study, we tested the expression of Piezo1 in PDAC cell lines and tissues, and cell apoptosis in vitro and in vivo with siRNA, a lentivirus system, and a subcutaneous xenograft tumor-bearing model under the condition of US with microbubbles (MBs). We found that Piezo1 was highly expressed in PDAC cells; it was activated by US with MBs and was closely related to the apoptosis of PDAC cell lines and tumors. This study highlighted the idea of utilizing the high expression of Piezo1 in PDAC and US with MBs to provide a non-invasive strategy for the treatment of PDAC from the aspect of mechanotransduction. Mechanosensitive channel Piezo1 is highly expressed in pancreatic cancer cells Ultrasound with microbubbles induces apoptosis of pancreatic cancer cells Piezo1 is activated by ultrasound with microbubbles and mediates calcium influx
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3
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Cui Q, Liu T, Li X, Zhao L, Wu Q, Wang X, Song K, Ge D. Validation of the mechano-bactericidal mechanism of nanostructured surfaces with finite element simulation. Colloids Surf B Biointerfaces 2021; 206:111929. [PMID: 34147928 DOI: 10.1016/j.colsurfb.2021.111929] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/02/2021] [Accepted: 06/14/2021] [Indexed: 10/21/2022]
Abstract
The mechano-bactericidal property of nanostructured surfaces has become the focus of intensive research toward the development of a new generation of antibacterial surfaces, especially in the current era of spreading antibiotic resistance. However, the mechanisms underlying nanostructured surfaces mechanically damaging bacteria remain unclear, which ultimately limits translational potential toward real-world applications. Using finite element simulation technique, we developed the three-dimensional thin wall with turgor pressure finite element model (3D-TWTP-FEM) of bacterial cell and verified the reliability of this model by the AFM indentation experiment simulation of the cell, and the cell model is able to simulate suspended bacterial cell and the process of cell adhering to the flat and nanopillar surfaces. Since bacterial cells suffer greater stress and deformation on the nanopillar surfaces, a two-stage model of the elastic and creep deformation stage of the cells on the nanostructured surfaces was developed. The calculations show that the location of the maximum stress/strain on the cells adhered to the nanopillar surfaces is at the liquid-cell-nanopillar three phase contact line. The computational results confirmed the ability of nanostructured surfaces to mechanically lyse bacteria and gave the effect of nanopillar geometry on the efficiency and speed of bacterial cell rupture. This study provides fundamental physical insights into how nanopillar surfaces can serve as effective and fast mechanical antimicrobial materials.
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Affiliation(s)
- Qianqian Cui
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Tianqing Liu
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China.
| | - Xiangqin Li
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Lidan Zhao
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Qiqi Wu
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Xin Wang
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Kedong Song
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
| | - Dan Ge
- School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, Liaoning Province, PR China
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4
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Jeong Y, Hong SJ, Cho SH, Yoon S, Lee H, Choi HK, Kim DM, Lee CG, Cho S, Cho BK. Multi-Omic Analyses Reveal Habitat Adaptation of Marine Cyanobacterium Synechocystis sp. PCC 7338. Front Microbiol 2021; 12:667450. [PMID: 34054774 PMCID: PMC8155712 DOI: 10.3389/fmicb.2021.667450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 04/19/2021] [Indexed: 11/13/2022] Open
Abstract
Cyanobacteria are considered as promising microbial cell factories producing a wide array of bio-products. Among them, Synechocystis sp. PCC 7338 has the advantage of growing in seawater, rather than requiring arable land or freshwater. Nonetheless, how this marine cyanobacterium grows under the high salt stress condition remains unknown. Here, we determined its complete genome sequence with the embedded regulatory elements and analyzed the transcriptional changes in response to a high-salt environment. Complete genome sequencing revealed a 3.70 mega base pair genome and three plasmids with a total of 3,589 genes annotated. Differential RNA-seq and Term-seq data aligned to the complete genome provided genome-wide information on genetic regulatory elements, including promoters, ribosome-binding sites, 5'- and 3'-untranslated regions, and terminators. Comparison with freshwater Synechocystis species revealed Synechocystis sp. PCC 7338 genome encodes additional genes, whose functions are related to ion channels to facilitate the adaptation to high salt and high osmotic pressure. Furthermore, a ferric uptake regulator binding motif was found in regulatory regions of various genes including SigF and the genes involved in energy metabolism, suggesting the iron-regulatory network is connected to not only the iron acquisition, but also response to high salt stress and photosynthesis. In addition, the transcriptomics analysis demonstrated a cyclic electron transport through photosystem I was actively used by the strain to satisfy the demand for ATP under high-salt environment. Our comprehensive analyses provide pivotal information to elucidate the genomic functions and regulations in Synechocystis sp. PCC 7338.
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Affiliation(s)
- Yujin Jeong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Seong-Joo Hong
- Department of Biological Engineering, Inha University, Incheon, South Korea.,Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Sang-Hyeok Cho
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Seonghoon Yoon
- Department of Biological Engineering, Inha University, Incheon, South Korea.,Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Hookeun Lee
- Institute of Pharmaceutical Research, College of Pharmacy, Gachon University, Incheon, South Korea
| | | | - Dong-Myung Kim
- Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon, South Korea
| | - Choul-Gyun Lee
- Department of Biological Engineering, Inha University, Incheon, South Korea.,Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Suhyung Cho
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.,Innovative Biomaterials Center, KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Byung-Kwan Cho
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.,Innovative Biomaterials Center, KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.,Intelligent Synthetic Biology Center, Daejeon, South Korea
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5
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Zhang X, Zhang Y, Tang S, Ma S, Shen Y, Chen Y, Tong Q, Li Y, Yang J. Hydrophobic Gate of Mechanosensitive Channel of Large Conductance in Lipid Bilayers Revealed by Solid-State NMR Spectroscopy. J Phys Chem B 2021; 125:2477-2490. [DOI: 10.1021/acs.jpcb.0c07487] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Xuning Zhang
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yan Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Siyang Tang
- Children’s Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Shaojie Ma
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yang Shen
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Yanke Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiong Tong
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yuezhou Li
- Children’s Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Jun Yang
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
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6
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Gong K, Fang T, Wan T, Yan Y, Li W, Zhang J. Voltage-gated multilayer graphene nanochannel for K+/Na+ separation: A molecular dynamics study. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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Corin K, Bowie JU. How bilayer properties influence membrane protein folding. Protein Sci 2020; 29:2348-2362. [PMID: 33058341 DOI: 10.1002/pro.3973] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/07/2020] [Accepted: 10/09/2020] [Indexed: 01/24/2023]
Abstract
The question of how proteins manage to organize into a unique three-dimensional structure has been a major field of study since the first protein structures were determined. For membrane proteins, the question is made more complex because, unlike water-soluble proteins, the solvent is not homogenous or even unique. Each cell and organelle has a distinct lipid composition that can change in response to environmental stimuli. Thus, the study of membrane protein folding requires not only understanding how the unfolded chain navigates its way to the folded state, but also how changes in bilayer properties can affect that search. Here we review what we know so far about the impact of lipid composition on bilayer physical properties and how those properties can affect folding. A better understanding of the lipid bilayer and its effects on membrane protein folding is not only important for a theoretical understanding of the folding process, but can also have a practical impact on our ability to work with and design membrane proteins.
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Affiliation(s)
- Karolina Corin
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
| | - James U Bowie
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
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8
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Li Y, Hu Y, Wang J, Liu X, Zhang W, Sun L. Structural Insights into a Plant Mechanosensitive Ion Channel MSL1. Cell Rep 2020; 30:4518-4527.e3. [DOI: 10.1016/j.celrep.2020.03.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/16/2020] [Accepted: 03/10/2020] [Indexed: 02/08/2023] Open
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9
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Li J, Zhang X, Ashokkumar M, Liu D, Ding T. Molecular regulatory mechanisms of Escherichia coli O157:H7 in response to ultrasonic stress revealed by proteomic analysis. ULTRASONICS SONOCHEMISTRY 2020; 61:104835. [PMID: 31670254 DOI: 10.1016/j.ultsonch.2019.104835] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 09/22/2019] [Accepted: 10/20/2019] [Indexed: 06/10/2023]
Abstract
The antimicrobial effects of ultrasonic filed have been studied for years at the phenotypic level, but there is little research to reveal the molecular regulatory mechanisms underlying the phenotypes. In this study, isobaric tag for relative and absolute quantification (iTRAQ) proteome was applied to analyze the regulatory networks of Escherichia coli O157:H7 in response to ultrasonic stress in whole-genome scale. A total of 1856 differentially expressed proteins were identified, of which 1141 were significant up-regulated and 715 down-regulated compared with live control cells. The comprehensive proteome coverage analysis showed that ultrasonic filed influenced various metabolic pathways in Escherichia coli O157:H7 cells. The ultrasound-induced up-regulation of global stress response regulator RpoS, bacterial mechanosensitive channels and SOS response protein RecA were described from the molecular level for the first time. In addition, we proposed a possible action mechanism that the free radicals produced by acoustic cavitation might enter into cells via the activated mechanosensitive channels, leading to the elevated intracellular ROS level and subsequent cell death. Last but not the least, we illustrated the all-or-nothing phenomenon of power ultrasound might due to the destruction of crucial cell defensive systems, including heat shock proteins and oxidative response regulators. These new findings can let us understand the ultrasonic effects more deeply and will contribute to this area.
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Affiliation(s)
- Jiao Li
- Department of Food Science and Nutrition, National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang University, Hangzhou, Zhejiang 310058, China; Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Hangzhou, Zhejiang 310058, China
| | - Xinglin Zhang
- Department of Food Science and Nutrition, National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | | | - Donghong Liu
- Department of Food Science and Nutrition, National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang University, Hangzhou, Zhejiang 310058, China; Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Hangzhou, Zhejiang 310058, China
| | - Tian Ding
- Department of Food Science and Nutrition, National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang University, Hangzhou, Zhejiang 310058, China; Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Hangzhou, Zhejiang 310058, China.
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10
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Azulay H, Lutaty A, Qvit N. Approach for comparing protein structures and origami models. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183132. [PMID: 31738904 DOI: 10.1016/j.bbamem.2019.183132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 10/05/2019] [Accepted: 10/28/2019] [Indexed: 11/20/2022]
Abstract
The research fields of proteins and origami have intersected in the study of folding and de-novo design of proteins. However, there is limited knowledge on the analogy between protein structures and origami models. We propose a general approach for comparing protein structures with origami models, and present a test case, comparing transmembrane β-barrel and α-helical barrel with the Yoshimura and Kresling origami models. While both shapes and structures may look similar, we demonstrated that the β-barrel and the α-helical barrel are in agreement only with the shape and structural characteristics of the Kresling model. Through the analogy, it is explained how the structural characteristic can help the β-barrel and α-helical barrel to adjust length and diameter in response to changes in the membrane structure. However, such conformations only apply to the α-helical barrel, and the β-barrel, in spite of resembles to the Kresling model, remains stiff due to hydrogen bonds between the β-strands. Thus, our analysis suggests that there are similar patterns between protein structures and origami models and that the proposed approach may provide important insight on the role that the structure of a protein fulfils, and on the preferred structural design of novel proteins with unique characteristics.
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Affiliation(s)
| | | | - Nir Qvit
- The Azrieli Faculty of Medicine in the Galilee, Bar-Ilan University, Henrietta Szold St. 8, POB 1589, Safed, Israel.
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11
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Rickeard BW, Nguyen MHL, DiPasquale M, Yip CG, Baker H, Heberle FA, Zuo X, Kelley EG, Nagao M, Marquardt D. Transverse lipid organization dictates bending fluctuations in model plasma membranes. NANOSCALE 2020; 12:1438-1447. [PMID: 31746906 DOI: 10.1039/c9nr07977g] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Membrane undulations play a vital role in many biological processes, including the regulation of membrane protein activity. The asymmetric lipid composition of most biological membranes complicates theoretical description of these bending fluctuations, yet experimental data that would inform any such a theory is scarce. Here, we used neutron spin-echo (NSE) spectroscopy to measure the bending fluctuations of large unilamellar vesicles (LUV) having an asymmetric transbilayer distribution of high- and low-melting lipids. The asymmetric vesicles were prepared using cyclodextrin-mediated lipid exchange, and were composed of an outer leaflet enriched in egg sphingomyelin (ESM) and an inner leaflet enriched in 1-palmitoyl-2-oleoyl-phosphoethanolamine (POPE), which have main transition temperatures of 37 °C and 25 °C, respectively. The overall membrane bending rigidity was measured at three temperatures: 15 °C, where both lipids are in a gel state; 45 °C, where both lipids are in a fluid state; and 30 °C, where there is gel-fluid co-existence. Remarkably, the dynamics for the fluid asymmetric LUVs (aLUVs) at 30 °C and 45 °C do not follow trends predicted by their symmetric counterparts. At 30 °C, compositional asymmetry suppressed the bending fluctuations, with the asymmetric bilayer exhibiting a larger bending modulus than that of symmetric bilayers corresponding to either the outer or inner leaflet. We conclude that the compositional asymmetry and leaflet coupling influence the internal dissipation within the bilayer and result in membrane properties that cannot be directly predicted from corresponding symmetric bilayers.
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Affiliation(s)
- Brett W Rickeard
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada.
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12
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Shahane G, Ding W, Palaiokostas M, Azevedo HS, Orsi M. Interaction of Antimicrobial Lipopeptides with Bacterial Lipid Bilayers. J Membr Biol 2019; 252:317-329. [PMID: 31098677 PMCID: PMC6790193 DOI: 10.1007/s00232-019-00068-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/03/2019] [Indexed: 02/07/2023]
Abstract
The resistance of pathogens to traditional antibiotics is currently a global issue of enormous concern. As the discovery and development of new antibiotics become increasingly challenging, synthetic antimicrobial lipopeptides (AMLPs) are now receiving renewed attention as a new class of antimicrobial agents. In contrast to traditional antibiotics, AMLPs act by physically disrupting the cell membrane (rather than targeting specific proteins), thus reducing the risk of inducing bacterial resistance. In this study, we use microsecond-timescale atomistic molecular dynamics simulations to quantify the interaction of a short AMLP (C16-KKK) with model bacterial lipid bilayers. In particular, we investigate how fundamental transmembrane properties change in relation to a range of lipopeptide concentrations. A number of structural, mechanical, and dynamical features are found to be significantly altered in a non-linear fashion. At 10 mol% concentration, lipopeptides have a condensing effect on bacterial bilayers, characterized by a decrease in the area per lipid and an increase in the bilayer order. Higher AMLP concentrations of 25 and 40 mol% destabilize the membrane by disrupting the bilayer core structure, inducing membrane thinning and water leakage. Important transmembrane properties such as the lateral pressure and dipole potential profiles are also affected. Potential implications on membrane function and associated proteins are discussed.
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Affiliation(s)
- Ganesh Shahane
- Institute of Bioengineering, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Wei Ding
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Michail Palaiokostas
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Helena S Azevedo
- School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Mario Orsi
- Department of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
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13
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Katsuta H, Sawada Y, Sokabe M. Biophysical Mechanisms of Membrane-Thickness-Dependent MscL Gating: An All-Atom Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7432-7442. [PMID: 30113845 DOI: 10.1021/acs.langmuir.8b02074] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The bacterial mechanosensitive channel, MscL, is activated by membrane tension, acting as a safety valve to prevent cell lysis against hypotonic challenge. It has been established that its activation threshold decreases with membrane thickness, while the underlying mechanism remains to be solved. We performed all-atom molecular dynamics (MD) simulations for the initial opening process of MscL embedded in four different types of lipid bilayers with different thicknesses: 1,2-dilauroyl- sn-glycero-3-phosphocholine (DLPC)), 1,2-dimyristoyl-glycero-3-phosphorylcholine (DMPC), 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), and 1,2-distearoyl- sn-glycero-3-phosphocholine (DSPC). In response to membrane stretching, channel opening occurred only in the thinner membranes (DLPC and DMPC) in a thickness-dependent way. We found that the MscL opening was governed by the rate and degree of membrane thinning and that the channel opening was tightly associated with the tilting of transmembrane (TM) helices of MscL toward the membrane plane. Upon membrane stretching, the order parameter of acyl chains of thinner membranes (DLPC and DMPC) became smaller, whereas other thicker membranes (DPPC and DSPC) showed interdigitation with little changes in the order parameter. The decreased order parameter contributed much more to membrane thinning than did interdigitation. We conclude that the membrane-thickness-dependent MscL opening mainly arises from structural changes in MscL to match the altered membrane thickness by stretching.
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14
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Rasmussen T, Rasmussen A, Yang L, Kaul C, Black S, Galbiati H, Conway SJ, Miller S, Blount P, Booth IR. Interaction of the Mechanosensitive Channel, MscS, with the Membrane Bilayer through Lipid Intercalation into Grooves and Pockets. J Mol Biol 2019; 431:3339-3352. [PMID: 31173776 DOI: 10.1016/j.jmb.2019.05.043] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/14/2019] [Accepted: 05/29/2019] [Indexed: 10/26/2022]
Abstract
All membrane proteins have dynamic and intimate relationships with the lipids of the bilayer that may determine their activity. Mechanosensitive channels sense tension through their interaction with the lipids of the membrane. We have proposed a mechanism for the bacterial channel of small conductance, MscS, that envisages variable occupancy of pockets in the channel by lipid chains. Here, we analyze protein-lipid interactions for MscS by quenching of tryptophan fluorescence with brominated lipids. By this strategy, we define the limits of the bilayer for TM1, which is the most lipid exposed helix of this protein. In addition, we show that residues deep in the pockets, created by the oligomeric assembly, interact with lipid chains. On the cytoplasmic side, lipids penetrate as far as the pore-lining helices and lipid molecules can align along TM3b perpendicular to lipids in the bilayer. Cardiolipin, free fatty acids, and branched lipids can access the pockets where the latter have a distinct effect on function. Cholesterol is excluded from the pockets. We demonstrate that introduction of hydrophilic residues into TM3b severely impairs channel function and that even "conservative" hydrophobic substitutions can modulate the stability of the open pore. The data provide important insights into the interactions between phospholipids and MscS and are discussed in the light of recent developments in the study of Piezo1 and TrpV4.
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Affiliation(s)
- Tim Rasmussen
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
| | - Akiko Rasmussen
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Limin Yang
- Department of Physiology, U.T. Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9040, USA.
| | - Corinna Kaul
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Susan Black
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Heloisa Galbiati
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Stuart J Conway
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.
| | - Samantha Miller
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
| | - Paul Blount
- Department of Physiology, U.T. Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9040, USA.
| | - Ian Rylance Booth
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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15
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Mallikarjunaiah KJ, Kinnun JJ, Petrache HI, Brown MF. Flexible lipid nanomaterials studied by NMR spectroscopy. Phys Chem Chem Phys 2019; 21:18422-18457. [DOI: 10.1039/c8cp06179c] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Advances in solid-state nuclear magnetic resonance spectroscopy inform the emergence of material properties from atomistic-level interactions in membrane lipid nanostructures.
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Affiliation(s)
- K. J. Mallikarjunaiah
- Department of Chemistry and Biochemistry
- University of Arizona
- Tucson
- USA
- Department of Physics
| | - Jacob J. Kinnun
- Department of Physics
- Indiana University-Purdue University
- Indianapolis
- USA
| | - Horia I. Petrache
- Department of Physics
- Indiana University-Purdue University
- Indianapolis
- USA
| | - Michael F. Brown
- Department of Chemistry and Biochemistry
- University of Arizona
- Tucson
- USA
- Department of Physics
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16
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Bucur FI, Grigore-Gurgu L, Crauwels P, Riedel CU, Nicolau AI. Resistance of Listeria monocytogenes to Stress Conditions Encountered in Food and Food Processing Environments. Front Microbiol 2018; 9:2700. [PMID: 30555426 PMCID: PMC6282059 DOI: 10.3389/fmicb.2018.02700] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/23/2018] [Indexed: 12/17/2022] Open
Abstract
Listeria monocytogenes is a human food-borne facultative intracellular pathogen that is resistant to a wide range of stress conditions. As a consequence, L. monocytogenes is extremely difficult to control along the entire food chain from production to storage and consumption. Frequent and recent outbreaks of L. monocytogenes infections illustrate that current measures of decontamination and preservation are suboptimal to control L. monocytogenes in food. In order to develop efficient measures to prevent contamination during processing and control growth during storage of food it is crucial to understand the mechanisms utilized by L. monocytogenes to tolerate the stress conditions in food matrices and food processing environments. Food-related stress conditions encountered by L. monocytogenes along the food chain are acidity, oxidative and osmotic stress, low or high temperatures, presence of bacteriocins and other preserving additives, and stresses as a consequence of applying alternative decontamination and preservation technologies such high hydrostatic pressure, pulsed and continuous UV light, pulsed electric fields (PEF). This review is aimed at providing a summary of the current knowledge on the response of L. monocytogenes toward these stresses and the mechanisms of stress resistance employed by this important food-borne bacterium. Circumstances when L. monocytogenes cells become more sensitive or more resistant are mentioned and existence of a cross-resistance when multiple stresses are present is pointed out.
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Affiliation(s)
- Florentina Ionela Bucur
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
| | - Leontina Grigore-Gurgu
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
| | - Peter Crauwels
- Institute of Microbiology and Biotechnology, Ulm University, Ulm, Germany
| | | | - Anca Ioana Nicolau
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Galati, Romania
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17
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Youkharibache P, Veretnik S, Li Q, Stanek KA, Mura C, Bourne PE. The Small β-Barrel Domain: A Survey-Based Structural Analysis. Structure 2018; 27:6-26. [PMID: 30393050 DOI: 10.1016/j.str.2018.09.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 06/12/2018] [Accepted: 09/19/2018] [Indexed: 11/27/2022]
Abstract
The small β-barrel (SBB) is an ancient protein structural domain characterized by extremes: it features a broad range of structural varieties, a deeply intricate evolutionary history, and it is associated with a bewildering array of cellular pathways. Here, we present a thorough, survey-based analysis of the structural properties of SBBs. We first consider the defining properties of the SBB, including various systems of nomenclature used to describe it, and we introduce the unifying concept of an "urfold." To begin elucidating how vast functional diversity can be achieved by a relatively simple domain, we explore the anatomy of the SBB and its representative structural variants. Many SBB proteins assemble into cyclic oligomers as the biologically functional units; these oligomers often bind RNA, and typically exhibit great quaternary structural plasticity (homomeric and heteromeric rings, variable subunit stoichiometries, etc.). We conclude with three themes that emerge from the rich structure ↔ function versatility of the SBB.
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Affiliation(s)
- Philippe Youkharibache
- National Center for Biotechnology Information, The National Library of Medicine, The National Institutes of Health, Bethesda, MD 20894, USA
| | - Stella Veretnik
- National Center for Biotechnology Information, The National Library of Medicine, The National Institutes of Health, Bethesda, MD 20894, USA.
| | - Qingliang Li
- National Center for Biotechnology Information, The National Library of Medicine, The National Institutes of Health, Bethesda, MD 20894, USA
| | - Kimberly A Stanek
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Cameron Mura
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA.
| | - Philip E Bourne
- National Center for Biotechnology Information, The National Library of Medicine, The National Institutes of Health, Bethesda, MD 20894, USA.
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18
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Abstract
Mechanosensitive (MS) channels protect bacteria against hypo-osmotic shock and fulfil additional functions. Hypo-osmotic shock leads to high turgor pressure that can cause cell rupture and death. MS channels open under these conditions and release unspecifically solutes and consequently the turgor pressure. They can recognise the raised pressure via the increased tension in the cell membrane. Currently, a better understanding how MS channels can sense tension on molecular level is developing because the interaction of the lipid bilayer with the channel is being investigated in detail. The MS channel of large conductance (MscL) and of small conductance (MscS) have been distinguished and studied in molecular detail. In addition, larger channels were found that contain a homologous region corresponding to MscS so that MscS represents a family of channels. Often several members of this family are present in a species. The importance of this family is underlined by the fact that members can be found not only in bacteria but also in higher organisms. While MscL and MscS have been studied for years in particular by electrophysiology, mutagenesis, molecular dynamics, X-ray crystallography and other biophysical techniques, only recently more details are emerging about other members of the MscS-family.
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19
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Howard RJ, Carnevale V, Delemotte L, Hellmich UA, Rothberg BS. Permeating disciplines: Overcoming barriers between molecular simulations and classical structure-function approaches in biological ion transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:927-942. [PMID: 29258839 DOI: 10.1016/j.bbamem.2017.12.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 12/08/2017] [Accepted: 12/14/2017] [Indexed: 11/20/2022]
Abstract
Ion translocation across biological barriers is a fundamental requirement for life. In many cases, controlling this process-for example with neuroactive drugs-demands an understanding of rapid and reversible structural changes in membrane-embedded proteins, including ion channels and transporters. Classical approaches to electrophysiology and structural biology have provided valuable insights into several such proteins over macroscopic, often discontinuous scales of space and time. Integrating these observations into meaningful mechanistic models now relies increasingly on computational methods, particularly molecular dynamics simulations, while surfacing important challenges in data management and conceptual alignment. Here, we seek to provide contemporary context, concrete examples, and a look to the future for bridging disciplinary gaps in biological ion transport. This article is part of a Special Issue entitled: Beyond the Structure-Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.
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Affiliation(s)
- Rebecca J Howard
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Box 1031, 17121 Solna, Sweden.
| | - Vincenzo Carnevale
- Institute for Computational Molecular Science, Department of Chemistry, Temple University, Philadelphia, PA 19122, USA.
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Theoretical Physics, KTH Royal Institute of Technology, Box 1031, 17121 Solna, Sweden.
| | - Ute A Hellmich
- Johannes Gutenberg University Mainz, Institute for Pharmacy and Biochemistry, Johann-Joachim-Becherweg 30, 55128 Mainz, Germany; Centre for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue Str. 9, 60438 Frankfurt, Germany.
| | - Brad S Rothberg
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA.
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20
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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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21
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Song Y, Zhang B, Guo F, Yang M, Li Y, Liu ZQ. Identification of Intracellular β-Barrel Residues Involved in Ion Selectivity in the Mechanosensitive Channel of Thermoanaerobacter tengcongensis. Front Physiol 2017; 8:832. [PMID: 29118717 PMCID: PMC5661003 DOI: 10.3389/fphys.2017.00832] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 10/06/2017] [Indexed: 11/13/2022] Open
Abstract
The mechanosensitive channel of small conductance (MscS) is a bacterial membrane pore that senses membrane tension and protects cells from lysis by releasing osmolytes. MscS is a homoheptameric channel with a cytoplasmic domain with seven portals and a β-barrel opening to the cytoplasm. TtMscS, an MscS channel from Thermoanaerobacter tengcongensis, is an anion-selective channel. A previous study from our laboratory has defined the crucial role of β-barrel in the anion selectivity of TtMscS (Zhang et al., 2012). However, the mechanistic details by which the β-barrel determines anion selectivity remain unclear. Here, using mutagenesis and patch-clamp recordings, we investigated the function and structural correlations between β-barrels and the anion selectivity of TtMscS at the atomic level. Our results indicated that mutation of V274, a residue at the center of the inner wall of the β-barrel in TtMscS, caused the anion selectivity of TtMscS reverse to cation selectivity. Moreover, the electrostatic potential (T272) and physical size (L276) of residues in the inner wall of β-barrel also determine the anion selectivity of TtMscS. In summary, the present study confirmed that the β-barrel region of TtMscS acts as a “selective filter” that renders TtMscS anion selectivity.
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Affiliation(s)
- Yingcai Song
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China
| | - Bing Zhang
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Fei Guo
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Maojun Yang
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yang Li
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Zhi-Qiang Liu
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China
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22
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Scholz N, Monk KR, Kittel RJ, Langenhan T. Adhesion GPCRs as a Putative Class of Metabotropic Mechanosensors. Handb Exp Pharmacol 2017; 234:221-247. [PMID: 27832490 DOI: 10.1007/978-3-319-41523-9_10] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Adhesion GPCRs as mechanosensors. Different aGPCR homologs and their cognate ligands have been described in settings, which suggest that they function in a mechanosensory capacity. For details, see text G protein-coupled receptors (GPCRs) constitute the most versatile superfamily of biosensors. This group of receptors is formed by hundreds of GPCRs, each of which is tuned to the perception of a specific set of stimuli a cell may encounter emanating from the outside world or from internal sources. Most GPCRs are receptive for chemical compounds such as peptides, proteins, lipids, nucleotides, sugars, and other organic compounds, and this capacity is utilized in several sensory organs to initiate visual, olfactory, gustatory, or endocrine signals. In contrast, GPCRs have only anecdotally been implicated in the perception of mechanical stimuli. Recent studies, however, show that the family of adhesion GPCRs (aGPCRs), which represents a large panel of over 30 homologs within the GPCR superfamily, displays molecular design and expression patterns that are compatible with receptivity toward mechanical cues (Fig. 1). Here, we review physiological and molecular principles of established mechanosensors, discuss their relevance for current research of the mechanosensory function of aGPCRs, and survey the current state of knowledge on aGPCRs as mechanosensing molecules.
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Affiliation(s)
- Nicole Scholz
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Röntgenring 9, Würzburg, 97070, Germany.
| | - Kelly R Monk
- Department of Developmental Biology, Hope Center for Neurologic Disorders, Washington University School of Medicine, St. Louis, 63110, MO, USA
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Röntgenring 9, Würzburg, 97070, Germany
| | - Tobias Langenhan
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Röntgenring 9, Würzburg, 97070, Germany.
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23
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Goldman RP, Jozefkowicz C, Canessa Fortuna A, Sutka M, Alleva K, Ozu M. Tonoplast (BvTIP1;2) and plasma membrane (BvPIP2;1) aquaporins show different mechanosensitive properties. FEBS Lett 2017; 591:1555-1565. [PMID: 28486763 DOI: 10.1002/1873-3468.12671] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/01/2017] [Accepted: 05/04/2017] [Indexed: 12/22/2022]
Abstract
Previous works proposed that aquaporins behave as mechanosensitive channels. However, principal issues about mechanosensitivity of aquaporins are not known. In this work, we characterized the mechanosensitive properties of the water channels BvTIP1;2 (TIP1) and BvPIP2;1 (PIP2) from red beet (Beta vulgaris). We simultaneously measured the mechanical behavior and the water transport rates during the osmotic response of emptied-out oocytes expressing TIP1 or PIP2. Our results indicate that TIP1 is a mechanosensitive aquaporin, whereas PIP2 is not. We found that a single exponential function between the osmotic permeability coefficient and the volumetric elastic modulus governs the mechanosensitivity of TIP1. Finally, homology modeling analysis indicates that putative residues involved in mechanosensitivity show different quantity and distribution in TIP1 and PIP2.
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Affiliation(s)
- Ramiro P Goldman
- Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Medicina, Instituto de Fisiología y Biofísica (IFIBIO Houssay), Laboratorio de Biomembranas, Universidad de Buenos Aires, Argentina
| | - Cintia Jozefkowicz
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Departamento de Fisicomatemática, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
| | - Agustina Canessa Fortuna
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Departamento de Fisicomatemática, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
| | - Moira Sutka
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - Karina Alleva
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Departamento de Fisicomatemática, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
| | - Marcelo Ozu
- Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Medicina, Instituto de Fisiología y Biofísica (IFIBIO Houssay), Laboratorio de Biomembranas, Universidad de Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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24
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Çetiner U, Rowe I, Schams A, Mayhew C, Rubin D, Anishkin A, Sukharev S. Tension-activated channels in the mechanism of osmotic fitness in Pseudomonas aeruginosa. J Gen Physiol 2017; 149:595-609. [PMID: 28424229 PMCID: PMC5412531 DOI: 10.1085/jgp.201611699] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 01/16/2017] [Accepted: 03/20/2017] [Indexed: 12/14/2022] Open
Abstract
Pseudomonas aeruginosa is resistant to drastic osmotic changes because of its ability to quickly jettison small osmolytes through osmotic release channels. Çetiner et al. reveal that it uses one MscL-like and at least two types of MscS-like channels during its osmotic response. Pseudomonas aeruginosa (PA) is an opportunistic pathogen with an exceptional ability to adapt to a range of environments. Part of its adaptive potential is the ability to survive drastic osmolarity changes. Upon a sudden dilution of external medium, such as during exposure to rain, bacteria evade mechanical rupture by engaging tension-activated channels that act as osmolyte release valves. In this study, we compare fast osmotic permeability responses in suspensions of wild-type PA and Escherichia coli (EC) strains in stopped-flow experiments and provide electrophysiological descriptions of osmotic-release channels in PA. Using osmotic dilution experiments, we first show that PA tolerates a broader range of shocks than EC. We record the kinetics of cell equilibration reported by light scattering responses to osmotic up- and down-shocks. PA exhibits a lower water permeability and faster osmolyte release rates during large osmotic dilutions than EC, which correlates with better survival. To directly characterize the PA tension-activated channels, we generate giant spheroplasts from this microorganism and record current responses in excised patches. Unlike EC, which relies primarily on two types of channels, EcMscS and EcMscL, to generate a distinctive two-wave pressure ramp response, PA exhibits a more gradual response that is dominated by MscL-type channels. Genome analysis, cloning, and expression reveal that PA possesses one MscL-type (PaMscL) and two MscS-type (PaMscS-1 and 2) proteins. In EC spheroplasts, both PaMscS channels exhibit a slightly earlier activation by pressure compared with EcMscS. Unitary currents reveal that PaMscS-2 has a smaller conductance, higher anionic preference, stronger inactivation, and slower recovery compared with PaMscS-1. We conclude that PA relies on MscL as the major valve defining a high rate of osmolyte release sufficient to curb osmotic swelling under extreme shocks, but it still requires MscS-type channels with a strong propensity to inactivation to properly terminate massive permeability response.
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Affiliation(s)
- Uğur Çetiner
- Department of Biology, University of Maryland, College Park, MD 20742.,Institute of Physical Science and Technology, University of Maryland, College Park, MD 20742.,Maryland Biophysics Program, University of Maryland, College Park, MD 20742
| | - Ian Rowe
- Department of Biology, University of Maryland, College Park, MD 20742.,Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742
| | - Anthony Schams
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Christina Mayhew
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Deanna Rubin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, MD 20742 .,Institute of Physical Science and Technology, University of Maryland, College Park, MD 20742.,Maryland Biophysics Program, University of Maryland, College Park, MD 20742
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25
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Curvature-Induced Spatial Ordering of Composition in Lipid Membranes. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2017; 2017:7275131. [PMID: 28473867 PMCID: PMC5394915 DOI: 10.1155/2017/7275131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/22/2017] [Indexed: 11/18/2022]
Abstract
Phase segregation of membranal components, such as proteins, lipids, and cholesterols, leads to the formation of aggregates or domains that are rich in specific constituents. This process is important in the interaction of the cell with its surroundings and in determining the cell's behavior and fate. Motivated by published experiments on curvature-modulated phase separation in lipid membranes, we formulate a mathematical model aiming at studying the spatial ordering of composition in a two-component biomembrane that is subjected to a prescribed (imposed) geometry. Based on this model, we identified key nondimensional quantities that govern the biomembrane response and performed numerical simulations to quantitatively explore their influence. We reproduce published experimental observations and extend them to surfaces with geometric features (imposed geometry) and lipid phases beyond those used in the experiments. In addition, we demonstrate the possibility for curvature-modulated phase separation above the critical temperature and propose a systematic procedure to determine which mechanism, the difference in bending stiffness or difference in spontaneous curvatures of the two phases, dominates the coupling between shape and composition.
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26
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27
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Argudo D, Bethel NP, Marcoline FV, Grabe M. Continuum descriptions of membranes and their interaction with proteins: Towards chemically accurate models. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1858:1619-34. [PMID: 26853937 PMCID: PMC4877259 DOI: 10.1016/j.bbamem.2016.02.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 01/30/2016] [Accepted: 02/01/2016] [Indexed: 01/21/2023]
Abstract
Biological membranes deform in response to resident proteins leading to a coupling between membrane shape and protein localization. Additionally, the membrane influences the function of membrane proteins. Here we review contributions to this field from continuum elastic membrane models focusing on the class of models that couple the protein to the membrane. While it has been argued that continuum models cannot reproduce the distortions observed in fully-atomistic molecular dynamics simulations, we suggest that this failure can be overcome by using chemically accurate representations of the protein. We outline our recent advances along these lines with our hybrid continuum-atomistic model, and we show the model is in excellent agreement with fully-atomistic simulations of the nhTMEM16 lipid scramblase. We believe that the speed and accuracy of continuum-atomistic methodologies will make it possible to simulate large scale, slow biological processes, such as membrane morphological changes, that are currently beyond the scope of other computational approaches. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- David Argudo
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, United States
| | - Neville P Bethel
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, United States
| | - Frank V Marcoline
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, United States
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, United States.
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28
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Saita E, Albanesi D, de Mendoza D. Sensing membrane thickness: Lessons learned from cold stress. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:837-846. [PMID: 26776056 DOI: 10.1016/j.bbalip.2016.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 01/06/2016] [Accepted: 01/07/2016] [Indexed: 10/22/2022]
Abstract
The lipid bilayer component of biological membranes is important for the distribution, organization, and function of bilayer spanning proteins. These physical barriers are subjected to bilayer perturbations. As a consequence, nature has evolved proteins that are able to sense changes in the bilayer properties and transform these lipid-mediated stimuli into intracellular signals. A structural feature that most signal-transducing membrane-embedded proteins have in common is one or more α-helices that traverse the lipid bilayer. Because of the interaction with the surrounding lipids, the organization of these transmembrane helices will be sensitive to membrane properties, like hydrophobic thickness. The helices may adapt to the lipids in different ways, which in turn can influence the structure and function of the intact membrane proteins. We review recent insights into the molecular basis of thermosensing via changes in membrane thickness and consider examples in which the hydrophobic matching can be demonstrated using reconstituted membrane systems. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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Affiliation(s)
- Emilio Saita
- Laboratorio de Fisiología Microbiana, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario. Ocampo y Esmeralda, Predio CONICET Rosario, 2000 Rosario, Argentina
| | - Daniela Albanesi
- Laboratorio de Fisiología Microbiana, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario. Ocampo y Esmeralda, Predio CONICET Rosario, 2000 Rosario, Argentina
| | - Diego de Mendoza
- Laboratorio de Fisiología Microbiana, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario. Ocampo y Esmeralda, Predio CONICET Rosario, 2000 Rosario, Argentina.
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29
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Abstract
Mechanotransduction, the conversion of physical forces into biochemical signals, is essential for various physiological processes such as the conscious sensations of touch and hearing, and the unconscious sensation of blood flow. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels.
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Affiliation(s)
- Sanjeev S Ranade
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ruhma Syeda
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ardem Patapoutian
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA.
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30
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Pliotas C, Dahl ACE, Rasmussen T, Mahendran KR, Smith TK, Marius P, Gault J, Banda T, Rasmussen A, Miller S, Robinson CV, Bayley H, Sansom MSP, Booth IR, Naismith JH. The role of lipids in mechanosensation. Nat Struct Mol Biol 2015; 22:991-8. [PMID: 26551077 PMCID: PMC4675090 DOI: 10.1038/nsmb.3120] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022]
Abstract
The ability of proteins to sense membrane tension is pervasive in biology. A higher-resolution structure of the Escherichia coli small-conductance mechanosensitive channel MscS identifies alkyl chains inside pockets formed by the transmembrane helices (TMs). Purified MscS contains E. coli lipids, and fluorescence quenching demonstrates that phospholipid acyl chains exchange between bilayer and TM pockets. Molecular dynamics and biophysical analyses show that the volume of the pockets and thus the number of lipid acyl chains within them decreases upon channel opening. Phospholipids with one acyl chain per head group (lysolipids) displace normal phospholipids (with two acyl chains) from MscS pockets and trigger channel opening. We propose that the extent of acyl-chain interdigitation in these pockets determines the conformation of MscS. When interdigitation is perturbed by increased membrane tension or by lysolipids, the closed state becomes unstable, and the channel gates.
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Affiliation(s)
- Christos Pliotas
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | | | - Tim Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Terry K Smith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Phedra Marius
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Joseph Gault
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Thandiwe Banda
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Akiko Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Samantha Miller
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Hagan Bayley
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Ian R Booth
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
- State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China
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31
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Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion. Proc Natl Acad Sci U S A 2015; 112:10726-31. [PMID: 26261325 PMCID: PMC4553819 DOI: 10.1073/pnas.1503202112] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 Å wide, exhibiting a large unitary conductance of ∼ 3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an ω-shaped loop and a short β-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands.
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32
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Modulating bilayer mechanical properties to promote the coupled folding and insertion of an integral membrane protein. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:503-12. [DOI: 10.1007/s00249-015-1032-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/23/2015] [Accepted: 05/05/2015] [Indexed: 12/17/2022]
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33
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Foo YH, Gao Y, Zhang H, Kenney LJ. Cytoplasmic sensing by the inner membrane histidine kinase EnvZ. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 118:119-29. [PMID: 25937465 DOI: 10.1016/j.pbiomolbio.2015.04.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 04/21/2015] [Accepted: 04/22/2015] [Indexed: 12/22/2022]
Abstract
Two-component regulatory systems drive signal transduction in bacteria. The simplest of these employs a membrane sensor kinase and a cytoplasmic response regulator. Environmental sensing is typically coupled to gene regulation. The histidine kinase EnvZ and its cognate response regulator OmpR regulate expression of outer membrane proteins (porins) in response to osmotic stress. We used hydrogen:deuterium exchange mass spectrometry to identify conformational changes in the cytoplasmic domain of EnvZ (EnvZc) that were associated with osmosensing. The osmosensor localized to a seventeen amino acid region of the four-helix bundle of the cytoplasmic domain and flanked the His(243) autophosphorylation site. High osmolality increased autophosphorylation of His(243), suggesting that these two events were linked. The transmembrane domains were not required for osmosensing, but mutants in the transmembrane domains altered EnvZ activity. A photoactivatable fusion protein composed of EnvZc fused to the fluorophore mEos2 (EnvZc-mEos2) was as capable as EnvZc in supporting OmpR-dependent ompF and ompC transcription. Over-expression of EnvZc reduced activity, indicating that the EnvZ/OmpR system is not robust. Our results support a model in which osmolytes stabilize helix one in the four-helix bundle of EnvZ by increased hydrogen bonding of the peptide backbone, increasing autophosphorylation and downstream signaling. The likelihood that additional histidine kinases use similar cytoplasmic sensing mechanisms is discussed.
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Affiliation(s)
- Yong Hwee Foo
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Yunfeng Gao
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Hongfang Zhang
- Mechanobiology Institute, National University of Singapore, Singapore
| | - Linda J Kenney
- Mechanobiology Institute, National University of Singapore, Singapore; Jesse Brown Veterans Affairs Medical Center, Chicago, USA; University of Illinois-Chicago, USA.
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34
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Saita EA, de Mendoza D. Thermosensing via transmembrane protein-lipid interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1757-64. [PMID: 25906947 DOI: 10.1016/j.bbamem.2015.04.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 11/25/2022]
Abstract
Cell membranes are composed of a lipid bilayer containing proteins that cross and/or interact with lipids on either side of the two leaflets. The basic structure of cell membranes is this bilayer, composed of two opposing lipid monolayers with fascinating properties designed to perform all the functions the cell requires. To coordinate these functions, lipid composition of cellular membranes is tailored to suit their specialized tasks. In this review, we describe the general mechanisms of membrane-protein interactions and relate them to some of the molecular strategies organisms use to adjust the membrane lipid composition in response to a decrease in environmental temperature. While the activities of all biomolecules are altered as a function of temperature, the thermosensors we focus on here are molecules whose temperature sensitivity appears to be linked to changes in the biophysical properties of membrane lipids. This article is part of a Special Issue entitled: Lipid-protein interactions.
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Affiliation(s)
- Emilio A Saita
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Predio CONICET, 2000-Rosario, Argentina
| | - Diego de Mendoza
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Predio CONICET, 2000-Rosario, Argentina.
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35
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Chandramouli B, Di Maio D, Mancini G, Barone V, Brancato G. Breaking the hydrophobicity of the MscL pore: insights into a charge-induced gating mechanism. PLoS One 2015; 10:e0120196. [PMID: 25825909 PMCID: PMC4380313 DOI: 10.1371/journal.pone.0120196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/06/2015] [Indexed: 01/17/2023] Open
Abstract
The mechanosensitive channel of large conductance (MscL) is a protein that responds to membrane tension by opening a transient pore during osmotic downshock. Due to its large pore size and functional reconstitution into lipid membranes, MscL has been proposed as a promising artificial nanovalve suitable for biotechnological applications. For example, site-specific mutations and tailored chemical modifications have shown how MscL channel gating can be triggered in the absence of tension by introducing charged residues at the hydrophobic pore level. Recently, engineered MscL proteins responsive to stimuli like pH or light have been reported. Inspired by experiments, we present a thorough computational study aiming at describing, with atomistic detail, the artificial gating mechanism and the molecular transport properties of a light-actuated bacterial MscL channel, in which a charge-induced gating mechanism has been enabled through the selective cleavage of photo-sensitive alkylating agents. Properties such as structural transitions, pore dimension, ion flux and selectivity have been carefully analyzed. Besides, the effects of charge on alternative sites of the channel with respect to those already reported have been addressed. Overall, our results provide useful molecular insights into the structural events accompanying the engineered MscL channel gating and the interplay of electrostatic effects, channel opening and permeation properties. In addition, we describe how the experimentally observed ionic current in a single-subunit charged MscL mutant is obtained through a hydrophobicity breaking mechanism involving an asymmetric inter-subunit motion.
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Affiliation(s)
| | - Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Giordano Mancini
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
- * E-mail:
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36
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Elani Y, Purushothaman S, Booth PJ, Seddon JM, Brooks NJ, Law RV, Ces O. Measurements of the effect of membrane asymmetry on the mechanical properties of lipid bilayers. Chem Commun (Camb) 2015; 51:6976-9. [PMID: 25797170 DOI: 10.1039/c5cc00712g] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We detail an approach for constructing asymmetric membranes and characterising their mechanical properties, leading to the first measurement of the effect of asymmetry on lipid bilayer mechanics. Our results demonstrate that asymmetry induces a significant increase in rigidity compared to symmetric membranes. Given that all biological membranes are asymmetric our findings have profound implications for the role of this phenomenon in biology.
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Affiliation(s)
- Yuval Elani
- Department of Chemistry, Imperial College London, Exhibition Road, London, SW7 2AZ, UK.
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37
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Kim TJ, Joo C, Seong J, Vafabakhsh R, Botvinick EL, Berns MW, Palmer AE, Wang N, Ha T, Jakobsson E, Sun J, Wang Y. Distinct mechanisms regulating mechanical force-induced Ca²⁺ signals at the plasma membrane and the ER in human MSCs. eLife 2015; 4:e04876. [PMID: 25667984 PMCID: PMC4337650 DOI: 10.7554/elife.04876] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 01/21/2015] [Indexed: 12/21/2022] Open
Abstract
It is unclear that how subcellular organelles respond to external mechanical stimuli. Here, we investigated the molecular mechanisms by which mechanical force regulates Ca2+ signaling at endoplasmic reticulum (ER) in human mesenchymal stem cells. Without extracellular Ca2+, ER Ca2+ release is the source of intracellular Ca2+ oscillations induced by laser-tweezer-traction at the plasma membrane, providing a model to study how mechanical stimuli can be transmitted deep inside the cell body. This ER Ca2+ release upon mechanical stimulation is mediated not only by the mechanical support of cytoskeleton and actomyosin contractility, but also by mechanosensitive Ca2+ permeable channels on the plasma membrane, specifically TRPM7. However, Ca2+ influx at the plasma membrane via mechanosensitive Ca2+ permeable channels is only mediated by the passive cytoskeletal structure but not active actomyosin contractility. Thus, active actomyosin contractility is essential for the response of ER to the external mechanical stimuli, distinct from the mechanical regulation at the plasma membrane. DOI:http://dx.doi.org/10.7554/eLife.04876.001 Cells receive many signals from their environment, for example, when they are compressed or pulled about by neighboring cells. Information about these ‘mechanical stimuli’ can be transmitted within the cell to trigger changes in gene expression and cell behavior. When a cell receives a mechanical stimulus, it can activate the release of calcium ions from storage compartments within the cell, including from a compartment called the endoplasmic reticulum. Calcium ions can also enter the cell from outside via channels located in the membrane that surrounds the cell (the plasma membrane). Kim et al. investigated how mechanical forces are transmitted in a type of human cell called mesenchymal stem cells using optical tweezers to apply a gentle force to the outside of a cell. These tweezers use a laser to attract tiny objects, in this case a bead attached to proteins in the cell's outer membrane. The cell's response to this mechanical stimulation was measured using a sensor protein that fluoresces a different color when it binds to calcium ions. With this set-up, Kim et al. found that mesenchymal stem cells are able to transmit mechanical forces to different depths within the cell. The forces can travel deep to trigger the release of calcium ions from the endoplasmic reticulum. This process involves a network of protein fibers that criss-cross to support the structure of a cell—called the cytoskeleton—and also requires proteins that are associated with the cytoskeleton to contract. However, calcium ion entry through the plasma membrane due to a mechanical force does not require these contractile proteins—only the cytoskeleton is involved. These results demonstrate that the transmission of mechanical signals to different depths within mesenchymal stem cells involves different components. Future work should shed light on how these mechanical signals control gene expression and the development of mesenchymal stem cells. DOI:http://dx.doi.org/10.7554/eLife.04876.002
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Affiliation(s)
- Tae-Jin Kim
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Chirlmin Joo
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Jihye Seong
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Reza Vafabakhsh
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Elliot L Botvinick
- Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, Irvine, United States
| | - Michael W Berns
- Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, Irvine, United States
| | - Amy E Palmer
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Boulder, United States
| | - Ning Wang
- Department of Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Taekjip Ha
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Eric Jakobsson
- Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Jie Sun
- Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Yingxiao Wang
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
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38
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Vanegas JM, Arroyo M. Force transduction and lipid binding in MscL: a continuum-molecular approach. PLoS One 2014; 9:e113947. [PMID: 25437007 PMCID: PMC4250078 DOI: 10.1371/journal.pone.0113947] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/30/2014] [Indexed: 01/22/2023] Open
Abstract
The bacterial mechanosensitive channel MscL, a small protein mainly activated by membrane tension, is a central model system to study the transduction of mechanical stimuli into chemical signals. Mutagenic studies suggest that MscL gating strongly depends on both intra-protein and interfacial lipid-protein interactions. However, there is a gap between this detailed chemical information and current mechanical models of MscL gating. Here, we investigate the MscL bilayer-protein interface through molecular dynamics simulations, and take a combined continuum-molecular approach to connect chemistry and mechanics. We quantify the effect of membrane tension on the forces acting on the surface of the channel, and identify interactions that may be critical in the force transduction between the membrane and MscL. We find that the local stress distribution on the protein surface is largely asymmetric, particularly under tension, with the cytoplasmic side showing significantly larger and more localized forces, which pull the protein radially outward. The molecular interactions that mediate this behavior arise from hydrogen bonds between the electronegative oxygens in the lipid headgroup and a cluster of positively charged lysine residues on the amphipathic S1 domain and the C-terminal end of the second trans-membrane helix. We take advantage of this strong interaction (estimated to be 10–13 kT per lipid) to actuate the channel (by applying forces on protein-bound lipids) and explore its sensitivity to the pulling magnitude and direction. We conclude by highlighting the simple motif that confers MscL with strong anchoring to the bilayer, and its presence in various integral membrane proteins including the human mechanosensitive channel K2P1 and bovine rhodopsin.
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Affiliation(s)
- Juan M. Vanegas
- LaCàN, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
- * E-mail:
| | - Marino Arroyo
- LaCàN, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
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39
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The rate of osmotic downshock determines the survival probability of bacterial mechanosensitive channel mutants. J Bacteriol 2014; 197:231-7. [PMID: 25349158 DOI: 10.1128/jb.02175-14] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mechanosensitive (MS) channels allow cells to sense and respond to environmental changes. In bacteria, these channels are believed to protect against an osmotic shock. The physiological function of these channels has been characterized primarily by a standardized assay, where aliquots of batch-cultured cells are rapidly pipetted into a hypotonic medium. Under this method, it has been inferred many types of MS channels (MscS homologs in Escherichia coli) demonstrate limited effectiveness against shock, typically rescuing less than 10% of the cells when expressed at native levels. We introduce a single-cell-based assay which allows us to control how fast the osmolarity changes, over time scales ranging from a fraction of a second to several minutes. We find that the protection provided by MS channels depends strongly on the rate of osmotic change, revealing that, under a slow enough osmotic drop, MscS homologs can lead to survival rates comparable to those found in wild-type strains. Further, after the osmotic downshift, we observe multiple death phenotypes, which are inconsistent with the prevailing paradigm of how cells lyse. Both of these findings require a reevaluation of our basic understanding of the physiology of MS channels.
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40
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Effertz T, Scharr AL, Ricci AJ. The how and why of identifying the hair cell mechano-electrical transduction channel. Pflugers Arch 2014; 467:73-84. [PMID: 25241775 DOI: 10.1007/s00424-014-1606-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/28/2014] [Accepted: 09/01/2014] [Indexed: 01/10/2023]
Abstract
Identification of the auditory hair cell mechano-electrical transduction (hcMET) channel has been a major focus in the hearing research field since the 1980s when direct mechanical gating of a transduction channel was proposed (Corey and Hudspeth J Neurosci 3:962-976, 1983). To this day, the molecular identity of this channel remains controversial. However, many of the hcMET channel's properties have been characterized, including pore properties, calcium-dependent ion permeability, rectification, and single channel conductance. At this point, elucidating the molecular identity of the hcMET channel will provide new tools for understanding the mechanotransduction process. This review discusses the significance of identifying the hcMET channel, the difficulties associated with that task, as well as the establishment of clear criteria for this identification. Finally, we discuss potential candidate channels in light of these criteria.
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Affiliation(s)
- Thomas Effertz
- Department of Otolaryngology, School of Medicine, Stanford University, Stanford, CA, 94305, USA
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Peyronnet R, Tran D, Girault T, Frachisse JM. Mechanosensitive channels: feeling tension in a world under pressure. FRONTIERS IN PLANT SCIENCE 2014; 5:558. [PMID: 25374575 PMCID: PMC4204436 DOI: 10.3389/fpls.2014.00558] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 09/29/2014] [Indexed: 05/02/2023]
Abstract
Plants, like other organisms, are facing multiple mechanical constraints generated both in their tissues and by the surrounding environments. They need to sense and adapt to these forces throughout their lifetimes. To do so, different mechanisms devoted to force transduction have emerged. Here we focus on fascinating proteins: the mechanosensitive (MS) channels. Mechanosensing in plants has been described for centuries but the molecular identification of MS channels occurred only recently. This review is aimed at plant biologists and plant biomechanists who want to be introduced to MS channel identity, how they work and what they might do in planta? In this review, electrophysiological properties, regulations, and functions of well-characterized MS channels belonging to bacteria and animals are compared with those of plants. Common and specific properties are discussed. We deduce which tools and concepts from animal and bacterial fields could be helpful for improving our understanding of plant mechanotransduction. MS channels embedded in their plasma membrane are sandwiched between the cell wall and the cytoskeleton. The consequences of this peculiar situation are analyzed and discussed. We also stress how important it is to probe mechanical forces at cellular and subcellular levels in planta in order to reveal the intimate relationship linking the membrane with MS channel activity. Finally we will propose new tracks to help to reveal their physiological functions at tissue and plant levels.
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Affiliation(s)
- Rémi Peyronnet
- National Heart and Lung Institute, Imperial College LondonLondon, UK
| | - Daniel Tran
- Institut des Sciences du Végétal – Centre National de la Recherche Scientifique, Saclay Plant SciencesGif-sur-Yvette, France
| | - Tiffanie Girault
- Institut des Sciences du Végétal – Centre National de la Recherche Scientifique, Saclay Plant SciencesGif-sur-Yvette, France
| | - Jean-Marie Frachisse
- Institut des Sciences du Végétal – Centre National de la Recherche Scientifique, Saclay Plant SciencesGif-sur-Yvette, France
- *Correspondence: Jean-Marie Frachisse, Institut des Sciences du Végétal – Centre National de la Recherche Scientifique, Saclay Plant Sciences, Bat 22-23A, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France e-mail:
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Nanobody mediated crystallization of an archeal mechanosensitive channel. PLoS One 2013; 8:e77984. [PMID: 24205053 PMCID: PMC3804602 DOI: 10.1371/journal.pone.0077984] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 09/16/2013] [Indexed: 11/19/2022] Open
Abstract
Mechanosensitive channels (MS) are integral membrane proteins and allow bacteria to survive sudden changes in external osmolarity due to transient opening of their pores. The efflux of cytoplasmic osmolytes reduces the membrane tension and prevents membrane rupture. Therefore these channels serve as emergency valves when experiencing significant environmental stress. The preparation of high quality crystals of integral membrane proteins is a major bottleneck for structure determination by X-ray crystallography. Crystallization chaperones based on various protein scaffolds have emerged as promising tool to increase the crystallization probability of a selected target protein. So far archeal mechanosensitive channels of small conductance have resisted crystallization in our hands. To structurally analyse these channels, we selected nanobodies against an archeal MS channel after immunization of a llama with recombinant expressed, detergent solubilized and purified protein. Here we present the characterization of 23 different binders regarding their interaction with the channel protein using analytical gel filtration, western blotting and surface plasmon resonance. Selected nanobodies bound the target with affinities in the pico- to nanomolar range and some binders had a profound effect on the crystallization of the MS channel. Together with previous data we show that nanobodies are a versatile and valuable tool in structural biology by widening the crystallization space for highly challenging proteins, protein complexes and integral membrane proteins.
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Ksenia Guseva: Formation and Cooperative Behavior of Protein Complexes on the Cell Membrane. Cell Biochem Biophys 2013. [DOI: 10.1007/s12013-012-9420-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
The Martini force field is a coarse-grained force field suited for molecular dynamics simulations of biomolecular systems. The force field has been parameterized in a systematic way, based on the reproduction of partitioning free energies between polar and apolar phases of a large number of chemical compounds. In this chapter the methodology underlying the force field is presented together with details of its parameterization and limitations. Then currently available topologies are described with a short overview of the key elements of their parameterization. These include the new polarizable Martini water model. A set of three selected ongoing studies using the Martini force field is presented. Finally the latest lines of development are discussed.
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Maftouni N, Amininasab M, Vali M, Ejtehadi M, Kowsari F. A Molecular Dynamics Simulation Study of Nanomechanical Properties of Asymmetric Lipid Bilayer. J Membr Biol 2012; 246:67-73. [DOI: 10.1007/s00232-012-9505-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 09/19/2012] [Indexed: 11/30/2022]
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Structure and molecular mechanism of an anion-selective mechanosensitive channel of small conductance. Proc Natl Acad Sci U S A 2012; 109:18180-5. [PMID: 23074248 DOI: 10.1073/pnas.1207977109] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Mechanosensitive (MS) channels are universal cellular membrane pores. Bacterial MS channels, as typified by MS channel of small conductance (MscS) from Escherichia coli (EcMscS), release osmolytes under hypoosmotic conditions. MS channels are known to be ion selective to different extents, but the underlying mechanism remains poorly understood. Here we identify an anion-selective MscS channel from Thermoanaerobacter tengcongensis (TtMscS). The structure of TtMscS closely resembles that of EcMscS, but it lacks the large cytoplasmic equatorial portals found in EcMscS. In contrast, the cytoplasmic pore formed by the C-terminal β-barrel of TtMscS is larger than that of EcMscS and has a strikingly different pattern of electrostatic surface potential. Swapping the β-barrel region between TtMscS and EcMscS partially switches the ion selectivity. Our study defines the role of the β-barrel in the ion selection of an anion-selective MscS channel and provides a structural basis for understanding the ion selectivity of MscS channels.
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Sukharev S, Sachs F. Molecular force transduction by ion channels: diversity and unifying principles. J Cell Sci 2012; 125:3075-83. [PMID: 22797911 DOI: 10.1242/jcs.092353] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cells perceive force through a variety of molecular sensors, of which the mechanosensitive ion channels are the most efficient and act the fastest. These channels apparently evolved to prevent osmotic lysis of the cell as a result of metabolite accumulation and/or external changes in osmolarity. From this simple beginning, nature developed specific mechanosensitive enzymes that allow us to hear, maintain balance, feel touch and regulate many systemic variables, such as blood pressure. For a channel to be mechanosensitive it needs to respond to mechanical stresses by changing its shape between the closed and open states. In that way, forces within the lipid bilayer or within a protein link can do work on the channel and stabilize its state. Ion channels have the highest turnover rates of all enzymes, and they can act as both sensors and effectors, providing the necessary fluxes to relieve osmotic pressure, shift the membrane potential or initiate chemical signaling. In this Commentary, we focus on the common mechanisms by which mechanical forces and the local environment can regulate membrane protein structure, and more specifically, mechanosensitive ion channels.
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Affiliation(s)
- Sergei Sukharev
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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Petrov E, Rohde PR, Cornell B, Martinac B. The protective effect of osmoprotectant TMAO on bacterial mechanosensitive channels of small conductance MscS/MscK under high hydrostatic pressure. Channels (Austin) 2012; 6:262-71. [PMID: 22790324 PMCID: PMC3508905 DOI: 10.4161/chan.20833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Activity of the bacterial mechanosensitive channels of small conductance MscS/MscK of E. coli was investigated under high hydrostatic pressure (HHP) using the "flying-patch" patch-clamp technique. The channels were gated by negative pipette voltage and their open probability was measured at HHP of 0.1 to 80 MPa. The channel open probability decreased with increasing HHP. When the osmolyte methylamine N-oxide (TMAO) was applied to the cytoplasmic side of the inside-out excised membrane patches of E. coli giant spheroplasts the inhibitory effect of HHP on the channel activity was suppressed at pressures of up to 40 MPa. At 40 MPa and above the channel open probability decreased in a similar fashion with or without TMAO. Our study suggests that TMAO helps to counteract the effect of HHP up to 40 MPa on the MscS/MscK open state by "shielding" the cytoplasmic domain of the channels.
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Affiliation(s)
- Evgeny Petrov
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
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Nilius B, Honoré E. Sensing pressure with ion channels. Trends Neurosci 2012; 35:477-86. [PMID: 22622029 DOI: 10.1016/j.tins.2012.04.002] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 04/05/2012] [Accepted: 04/10/2012] [Indexed: 12/23/2022]
Abstract
Opening of stretch-activated ion channels (SACs) is the earliest event occurring in mechanosensory transduction. The molecular identity of mammalian SACs has long remained a mystery. Only very recently, Piezo1 and Piezo2 have been shown to be essential components of distinct SACs and moreover, purified Piezo1 forms cationic channels when reconstituted into artificial bilayers. In line with these findings, dPiezo was demonstrated to act in the Drosophila mechanical nociception pathway. Finally, the 3D structure of the two-pore domain potassium channel (K(2P)), TRAAK [weakly inward rectifying K⁺ channel (TWIK)-related arachidonic acid stimulated K⁺ channel], has recently been solved, providing valuable information about pharmacology, selectivity and gating mechanisms of stretch-activated K⁺ channels (SAKs). These recent findings allow a better understanding of the molecular basis of molecular and cellular mechanotransduction.
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Affiliation(s)
- Bernd Nilius
- Laboratory of Ion Channel Research, Department of Cell and Molecular Medicine, Katholieke Universiteit-KU Leuven, Campus Gasthuisberg, O&N 1, Herestraat 49-Bus 802, B-3000 Leuven, Belgium
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Lindén M, Sens P, Phillips R. Entropic tension in crowded membranes. PLoS Comput Biol 2012; 8:e1002431. [PMID: 22438801 PMCID: PMC3305330 DOI: 10.1371/journal.pcbi.1002431] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 02/01/2012] [Indexed: 11/18/2022] Open
Abstract
Unlike their model membrane counterparts, biological membranes are richly decorated with a heterogeneous assembly of membrane proteins. These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape controlling the conformational transitions suffered by such proteins. For membrane channels, this effect can alter the critical membrane tension at which they undergo a transition from a closed to an open state, and therefore influence protein function in vivo. Despite their obvious importance, crowding phenomena in membranes are much less well studied than in the cytoplasm. Using statistical mechanics results for hard disk liquids, we show that crowding induces an entropic tension in the membrane, which influences transitions that alter the projected area and circumference of a membrane protein. As a specific case study in this effect, we consider the impact of crowding on the gating properties of bacterial mechanosensitive membrane channels, which are thought to confer osmoprotection when these cells are subjected to osmotic shock. We find that crowding can alter the gating energies by more than in physiological conditions, a substantial fraction of the total gating energies in some cases. Given the ubiquity of membrane crowding, the nonspecific nature of excluded volume interactions, and the fact that the function of many membrane proteins involve significant conformational changes, this specific case study highlights a general aspect in the function of membrane proteins. Biological membranes are a complex array of lipids and proteins. The typical bacterial membrane is made up of hundreds of copies of different species of membrane proteins embedded in a sea of different types of lipids. One of the distinguishing features of biological matter is the high degree of “crowding” to which the different macromolecules are subjected. In this work, we explore the consequences of such crowding in the membrane setting, building upon earlier work which has primarily focused on how crowding affects properties in the cytoplasm. The particular case study considered here centers on a class of membrane channels which respond to tension in the cell membrane serving to provide osmoprotection to cells subjected to osmotic shock. We explore how the critical tension at which these channels open depends upon the concentration of other membrane proteins, and conclude that it can be significantly higher at physiological protein densities compared to the intrinsic value measured in protein free membranes.
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Affiliation(s)
- Martin Lindén
- Department of Applied Physics, California Institute of Technology, Pasadena, California, United States of America
| | - Pierre Sens
- Laboratoire de Physico-Chimie Théorique, CNRS/UMR 7083, ESPCI, Paris, France
| | - Rob Phillips
- Department of Applied Physics, California Institute of Technology, Pasadena, California, United States of America
- Laboratoire de Physico-Chimie Théorique, CNRS/UMR 7083, ESPCI, Paris, France
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
- * E-mail:
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