1
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Senapati S, Park PSH. Understanding the Rhodopsin Worldview Through Atomic Force Microscopy (AFM): Structure, Stability, and Activity Studies. CHEM REC 2023; 23:e202300113. [PMID: 37265335 PMCID: PMC10908267 DOI: 10.1002/tcr.202300113] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/12/2023] [Indexed: 06/03/2023]
Abstract
Rhodopsin is a G protein-coupled receptor (GPCR) present in the rod outer segment (ROS) of photoreceptor cells that initiates the phototransduction cascade required for scotopic vision. Due to the remarkable advancements in technological tools, the chemistry of rhodopsin has begun to unravel especially over the past few decades, but mostly at the ensemble scale. Atomic force microscopy (AFM) is a tool capable of providing critical information from a single-molecule point of view. In this regard, to bolster our understanding of rhodopsin at the nanoscale level, AFM-based imaging, force spectroscopy, and nano-indentation techniques were employed on ROS disc membranes containing rhodopsin, isolated from vertebrate species both in normal and diseased states. These AFM studies on samples from native retinal tissue have provided fundamental insights into the structure and function of rhodopsin under normal and dysfunctional states. We review here the findings from these AFM studies that provide important insights on the supramolecular organization of rhodopsin within the membrane and factors that contribute to this organization, the molecular interactions stabilizing the structure of the receptor and factors that can modify those interactions, and the mechanism underlying constitutive activity in the receptor that can cause disease.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
- Prayoga Institute of Education Research, Bengaluru, KA 560116, India
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
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2
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Wijesinghe WCB, Min D. Single-Molecule Force Spectroscopy of Membrane Protein Folding. J Mol Biol 2023; 435:167975. [PMID: 37330286 DOI: 10.1016/j.jmb.2023.167975] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 01/13/2023] [Accepted: 01/17/2023] [Indexed: 06/19/2023]
Abstract
Single-molecule force spectroscopy is a unique method that can probe the structural changes of single proteins at a high spatiotemporal resolution while mechanically manipulating them over a wide force range. Here, we review the current understanding of membrane protein folding learned by using the force spectroscopy approach. Membrane protein folding in lipid bilayers is one of the most complex biological processes in which diverse lipid molecules and chaperone proteins are intricately involved. The approach of single protein forced unfolding in lipid bilayers has produced important findings and insights into membrane protein folding. This review provides an overview of the forced unfolding approach, including recent achievements and technical advances. Progress in the methods can reveal more interesting cases of membrane protein folding and clarify general mechanisms and principles.
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Affiliation(s)
- W C Bhashini Wijesinghe
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Duyoung Min
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea; Center for Wave Energy Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
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3
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Fang B, Zhao L, Du X, Liu Q, Yang H, Li F, Sheng Y, Zhao W, Zhong H. Studying the
Rhodopsin‐Like
G Protein Coupled Receptors by Atomic Force Microscopy. Cytoskeleton (Hoboken) 2022; 78:400-416. [DOI: 10.1002/cm.21692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/09/2022] [Accepted: 01/13/2022] [Indexed: 11/10/2022]
Affiliation(s)
- Bin Fang
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Li Zhao
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Xiaowei Du
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Qiyuan Liu
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
- School of Basic Medicine Gannan Medical University Ganzhou People's Republic of China
| | - Hui Yang
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Fangzuo Li
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Yaohuan Sheng
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Weidong Zhao
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
| | - Haijian Zhong
- Key Laboratory of Biomaterials and Biofabrication in Tissue Engineering of Jiangxi Province Gannan Medical University Ganzhou People's Republic of China
- School of Medical Information Engineering Gannan Medical University Ganzhou People's Republic of China
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases, Ministry of Education Gannan Medical University Ganzhou People's Republic of China
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4
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Colozo AT, Vasudevan S, Park PSH. Retinal degeneration in mice expressing the constitutively active G90D rhodopsin mutant. Hum Mol Genet 2021; 29:881-891. [PMID: 31960909 DOI: 10.1093/hmg/ddaa008] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/11/2019] [Accepted: 01/15/2020] [Indexed: 11/13/2022] Open
Abstract
Rhodopsin is the G protein-coupled receptor in rod photoreceptor cells that initiates vision upon photon capture. The light receptor is normally locked in an inactive state in the dark by the covalently bound inverse agonist 11-cis retinal. Mutations can render the receptor active even in the absence of light. This constitutive activity can desensitize rod photoreceptor cells and lead to night blindness. A G90D mutation in rhodopsin causes the receptor to be constitutively active and leads to congenital stationary night blindness, which is generally thought to be devoid of retinal degeneration. The constitutively active species responsible for the night blindness phenotype is unclear. Moreover, the classification as a stationary disease devoid of retinal degeneration is also misleading. A transgenic mouse model for congenital stationary night blindness that expresses the G90D rhodopsin mutant was examined to better understand the origin of constitutive activity and the potential for retinal degeneration. Heterozygous mice for the G90D mutation did not exhibit retinal degeneration whereas homozygous mice exhibited progressive retinal degeneration. Only a modest reversal of retinal degeneration was observed when transducin signaling was eliminated genetically, indicating that some of the retinal degeneration occurred in a transducin-independent manner. Biochemical studies on purified rhodopsin from mice indicated that multiple species can potentially contribute to the constitutive activity causing night blindness.
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Affiliation(s)
- Alejandro T Colozo
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sreelakshmi Vasudevan
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
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5
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Senapati S, Poma AB, Cieplak M, Filipek S, Park PSH. Differentiating between Inactive and Active States of Rhodopsin by Atomic Force Microscopy in Native Membranes. Anal Chem 2019; 91:7226-7235. [PMID: 31074606 DOI: 10.1021/acs.analchem.9b00546] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Membrane proteins, including G protein-coupled receptors (GPCRs), present a challenge in studying their structural properties under physiological conditions. Moreover, to better understand the activity of proteins requires examination of single molecule behaviors rather than ensemble averaged behaviors. Force-distance curve-based AFM (FD-AFM) was utilized to directly probe and localize the conformational states of a GPCR within the membrane at nanoscale resolution based on the mechanical properties of the receptor. FD-AFM was applied to rhodopsin, the light receptor and a prototypical GPCR, embedded in native rod outer segment disc membranes from photoreceptor cells of the retina in mice. Both FD-AFM and computational studies on coarse-grained models of rhodopsin revealed that the active state of the receptor has a higher Young's modulus compared to the inactive state of the receptor. Thus, the inactive and active states of rhodopsin could be differentiated based on the stiffness of the receptor. Differentiating the states based on the Young's modulus allowed for the mapping of the different states within the membrane. Quantifying the active states present in the membrane containing the constitutively active G90D rhodopsin mutant or apoprotein opsin revealed that most receptors adopt an active state. Traditionally, constitutive activity of GPCRs has been described in terms of two-state models where the receptor can achieve only a single active state. FD-AFM data are inconsistent with a two-state model but instead require models that incorporate multiple active states.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Adolfo B Poma
- Institute of Fundamental Technological Research , Polish Academy of Sciences , Pawińskiego 5B , 02-106 Warsaw , Poland.,Institute of Physics , Polish Academy of Sciences , Aleja Lotników 32/46 , 02-668 Warsaw , Poland
| | - Marek Cieplak
- Institute of Physics , Polish Academy of Sciences , Aleja Lotników 32/46 , 02-668 Warsaw , Poland
| | - Sławomir Filipek
- Faculty of Chemistry, Biological and Chemical Research Centre , University of Warsaw , 02-093 Warsaw , Poland
| | - Paul S H Park
- Department of Ophthalmology and Visual Sciences , Case Western Reserve University , Cleveland , Ohio 44106 , United States
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6
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Senapati S, Gragg M, Samuels IS, Parmar VM, Maeda A, Park PSH. Effect of dietary docosahexaenoic acid on rhodopsin content and packing in photoreceptor cell membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1403-1413. [PMID: 29626443 DOI: 10.1016/j.bbamem.2018.03.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/13/2018] [Accepted: 03/30/2018] [Indexed: 01/03/2023]
Abstract
Docosahexaenoic acid (DHA) is enriched in photoreceptor cell membranes. DHA deficiency impairs vision due to photoreceptor cell dysfunction, which is caused, at least in part, by reduced activity of rhodopsin, the light receptor that initiates phototransduction. It is unclear how the depletion of membrane DHA impacts the structural properties of rhodopsin and, in turn, its activity. Atomic force microscopy (AFM) was used to assess the impact of DHA deficiency on membrane structure and rhodopsin organization. AFM revealed that signaling impairment in photoreceptor cells is independent of the oligomeric status of rhodopsin and causes adaptations in photoreceptor cells where the content and density of rhodopsin in the membrane is increased. Functional and structural changes caused by DHA deficiency were reversible.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Megan Gragg
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ivy S Samuels
- Research Service, Louis Stokes Cleveland Veterans Administration Medical Center, Cleveland, OH 44106, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Vipul M Parmar
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Akiko Maeda
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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7
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Characterization of mechanical unfolding intermediates of membrane proteins by coarse grained molecular dynamics simulation. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2017.11.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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8
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Maity S, Ilieva N, Laio A, Torre V, Mazzolini M. New views on phototransduction from atomic force microscopy and single molecule force spectroscopy on native rods. Sci Rep 2017; 7:12000. [PMID: 28931892 PMCID: PMC5607320 DOI: 10.1038/s41598-017-11912-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 08/25/2017] [Indexed: 12/11/2022] Open
Abstract
By combining atomic force microscopy (AFM) imaging and single-molecule force spectroscopy (SMFS), we analyzed membrane proteins of the rod outer segments (OS). With this combined approach we were able to study the membrane proteins in their natural environment. In the plasma membrane we identified native cyclic nucleotide-gated (CNG) channels which are organized in single file strings. We also identified rhodopsin located both in the discs and in the plasma membrane. SMFS reveals strikingly different mechanical properties of rhodopsin unfolding in the two environments. Molecular dynamic simulations suggest that this difference is likely to be related to the higher hydrophobicity of the plasma membrane, due to the higher cholesterol concentration. This increases rhodopsin mechanical stability lowering the rate of transition towards its active form, hindering, in this manner, phototransduction.
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Affiliation(s)
- Sourav Maity
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Nina Ilieva
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Alessandro Laio
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy
| | - Vincent Torre
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy.
| | - Monica Mazzolini
- International School for Advanced Studies (SISSA-ISAS) via Bonomea 265, 34136, Trieste, Italy.
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9
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Forced Unfolding Mechanism of Bacteriorhodopsin as Revealed by Coarse-Grained Molecular Dynamics. Biophys J 2017; 111:2086-2098. [PMID: 27851934 DOI: 10.1016/j.bpj.2016.09.051] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 09/23/2016] [Accepted: 09/26/2016] [Indexed: 12/18/2022] Open
Abstract
Developments in atomic force microscopy have opened up a new path toward single-molecular phenomena; in particular, during the process of pulling a membrane protein out of a lipid bilayer. However, the characteristic features of the force-distance (F-D) curve of a bacteriorhodopsin in purple membrane, for instance, have not yet been fully elucidated in terms of physicochemical principles. To address the issue, we performed a computer simulation of bacteriorhodopsin with, to our knowledge, a novel coarse-grained (C-G) model. Peptide planes are represented as rigid spheres, while the surrounding environment consisting of water solvents and lipid bilayers is represented as an implicit continuum. Force-field parameters were determined on the basis of auxiliary simulations and experimental values of transfer free energy of each amino acid from water to membrane. According to Popot's two-stage model, we separated molecular interactions involving membrane proteins into two parts: I) affinity of each amino acid to the membrane and intrahelical hydrogen bonding between main chain peptide bonds; and II) interhelix interactions. Then, only part I was incorporated into the C-G model because we assumed that the part plays a dominant role in the forced unfolding process. As a result, the C-G simulation has successfully reproduced the key features, including peak positions, of the experimental F-D curves in the literature, indicating that the peak positions are essentially determined by the residue-lipid and intrahelix interactions. Furthermore, we investigated the relationships between the energy barrier formation on the forced unfolding pathways and the force peaks of the F-D curves.
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10
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Tian H, Fürstenberg A, Huber T. Labeling and Single-Molecule Methods To Monitor G Protein-Coupled Receptor Dynamics. Chem Rev 2016; 117:186-245. [DOI: 10.1021/acs.chemrev.6b00084] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- He Tian
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Alexandre Fürstenberg
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Thomas Huber
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
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11
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Rhodopsin Forms Nanodomains in Rod Outer Segment Disc Membranes of the Cold-Blooded Xenopus laevis. PLoS One 2015; 10:e0141114. [PMID: 26492040 PMCID: PMC4619631 DOI: 10.1371/journal.pone.0141114] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 10/04/2015] [Indexed: 11/19/2022] Open
Abstract
Rhodopsin forms nanoscale domains (i.e., nanodomains) in rod outer segment disc membranes from mammalian species. It is unclear whether rhodopsin arranges in a similar manner in amphibian species, which are often used as a model system to investigate the function of rhodopsin and the structure of photoreceptor cells. Moreover, since samples are routinely prepared at low temperatures, it is unclear whether lipid phase separation effects in the membrane promote the observed nanodomain organization of rhodopsin from mammalian species. Rod outer segment disc membranes prepared from the cold-blooded frog Xenopus laevis were investigated by atomic force microscopy to visualize the organization of rhodopsin in the absence of lipid phase separation effects. Atomic force microscopy revealed that rhodopsin nanodomains form similarly as that observed previously in mammalian membranes. Formation of nanodomains in ROS disc membranes is independent of lipid phase separation and conserved among vertebrates.
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12
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Miller LM, Gragg M, Kim TG, Park PSH. Misfolded opsin mutants display elevated β-sheet structure. FEBS Lett 2015; 589:3119-25. [PMID: 26358292 DOI: 10.1016/j.febslet.2015.08.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 08/31/2015] [Indexed: 01/04/2023]
Abstract
Mutations in rhodopsin can cause misfolding and aggregation of the receptor, which leads to retinitis pigmentosa, a progressive retinal degenerative disease. The structure adopted by misfolded opsin mutants and the associated cell toxicity is poorly understood. Förster resonance energy transfer (FRET) and Fourier transform infrared (FTIR) microspectroscopy were utilized to probe within cells the structures formed by G188R and P23H opsins, which are misfolding mutants that cause autosomal dominant retinitis pigmentosa. Both mutants formed aggregates in the endoplasmic reticulum and exhibited altered secondary structure with elevated β-sheet and reduced α-helical content. The newly formed β-sheet structure may facilitate the aggregation of misfolded opsin mutants. The effects observed for the mutants were unrelated to retention of opsin molecules in the endoplasmic reticulum itself.
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Affiliation(s)
- Lisa M Miller
- National Synchrotron Light Source-II, Brookhaven National Laboratory, Upton, NY 11973, USA.
| | - Megan Gragg
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
| | - Tae Gyun Kim
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA.
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13
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Petrosyan R, Bippes CA, Walheim S, Harder D, Fotiadis D, Schimmel T, Alsteens D, Müller DJ. Single-molecule force spectroscopy of membrane proteins from membranes freely spanning across nanoscopic pores. NANO LETTERS 2015; 15:3624-3633. [PMID: 25879249 DOI: 10.1021/acs.nanolett.5b01223] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Single-molecule force spectroscopy (SMFS) provides detailed insight into the mechanical (un)folding pathways and structural stability of membrane proteins. So far, SMFS could only be applied to membrane proteins embedded in native or synthetic membranes adsorbed to solid supports. This adsorption causes experimental limitations and raises the question to what extent the support influences the results obtained by SMFS. Therefore, we introduce here SMFS from native purple membrane freely spanning across nanopores. We show that correct analysis of the SMFS data requires extending the worm-like chain model, which describes the mechanical stretching of a polypeptide, by the cubic extension model, which describes the bending of a purple membrane exposed to mechanical stress. This new experimental and theoretical approach allows to characterize the stepwise (un)folding of the membrane protein bacteriorhodopsin and to assign the stability of single and grouped secondary structures. The (un)folding and stability of bacteriorhodopsin shows no significant difference between freely spanning and directly supported purple membranes. Importantly, the novel experimental SMFS setup opens an avenue to characterize any protein from freely spanning cellular or synthetic membranes.
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Affiliation(s)
- Rafayel Petrosyan
- ‡Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, 4058 Basel, Switzerland
| | - Christian A Bippes
- ‡Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, 4058 Basel, Switzerland
| | - Stefan Walheim
- †Institute of Applied Physics and Center for Functional Nanostructures (CFN) and Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany
| | - Daniel Harder
- §Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland
| | - Dimitrios Fotiadis
- §Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland
| | - Thomas Schimmel
- †Institute of Applied Physics and Center for Functional Nanostructures (CFN) and Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany
| | - David Alsteens
- ‡Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, 4058 Basel, Switzerland
| | - Daniel J Müller
- ‡Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, 4058 Basel, Switzerland
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14
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Abstract
Membrane proteins are an important class of proteins in biology and therapeutics. Understanding the dynamic nature of the molecular interactions that stabilize membrane protein structure is critical to dissect the mechanism of action and dysfunction of these proteins. Single-molecule force spectroscopy (SMFS) and dynamic SMFS (DFS) are emerging nanotechniques that allow the study of membrane proteins under the physiologically relevant conditions of a lipid bilayer and buffer conditions. These techniques directly probe the molecular interactions underlying protein structure and reveal unique insights about their properties. Outlined in this report will be procedures on how to conduct SMFS and DFS on rhodopsin in native retinal membranes. Rhodopsin is a membrane protein belonging to the G protein-coupled receptor family of proteins, one of the largest families of proteins in nature.
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15
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Whited AM, Park PSH. Nanodomain organization of rhodopsin in native human and murine rod outer segment disc membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:26-34. [PMID: 25305340 DOI: 10.1016/j.bbamem.2014.10.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 09/25/2014] [Accepted: 10/01/2014] [Indexed: 01/31/2023]
Abstract
Biological membranes display distinct domains that organize membrane proteins and signaling molecules to facilitate efficient and reliable signaling. The organization of rhodopsin, a G protein-coupled receptor, in native rod outer segment disc membranes was investigated by atomic force microscopy. Atomic force microscopy revealed that rhodopsin is arranged into domains of variable size, which we refer to herein as nanodomains, in native membranes. Quantitative analysis of 150 disc membranes revealed that the physical properties of nanodomains are conserved in humans and mice and that the properties of individual disc membranes can be variable. Examining the variable properties of disc membranes revealed some of the factors contributing to the size of rod outer segment discs and the formation of nanodomains in the membrane. The diameter of rod outer segment discs was dependent on the number of rhodopsin molecules incorporated into the membrane but independent of the spatial density of rhodopsin. The number of nanodomains present in a single disc was also dependent on the number of rhodopsin molecules incorporated into the membrane. The size of the nanodomains was largely independent of the number or spatial density of rhodopsin in the membrane.
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Affiliation(s)
- Allison M Whited
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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16
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Orban T, Jastrzebska B, Palczewski K. Structural approaches to understanding retinal proteins needed for vision. Curr Opin Cell Biol 2013; 27:32-43. [PMID: 24680428 DOI: 10.1016/j.ceb.2013.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/31/2013] [Accepted: 11/01/2013] [Indexed: 12/21/2022]
Abstract
The past decade has witnessed an impressive expansion of our knowledge of retinal photoreceptor signal transduction and the regulation of the visual cycle required for normal eyesight. Progress in human genetics and next generation sequencing technologies have revealed the complexity behind many inherited retinal diseases. Structural studies have markedly increased our understanding of the visual process. Moreover, technical innovations and improved methodologies in proteomics, macromolecular crystallization and high resolution imaging at different levels set the scene for even greater advances. Pharmacology combined with structural biology of membrane proteins holds great promise for developing innovative accessible therapies for millions robbed of their sight or progressing toward blindness.
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Affiliation(s)
- Tivadar Orban
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Beata Jastrzebska
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA.
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17
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Zocher M, Bippes CA, Zhang C, Müller DJ. Single-molecule force spectroscopy of G-protein-coupled receptors. Chem Soc Rev 2013; 42:7801-15. [PMID: 23799399 DOI: 10.1039/c3cs60085h] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The applicability of single-molecule force spectroscopy (SMFS) to characterize membrane proteins in vitro is developing rapidly and opening a wide range of fascinating possibilities to study how intra- and intermolecular interactions determine their structural stability and functional state. In particular, understanding how molecular interactions contribute to the functional state of G-protein-coupled receptors (GPCRs) is of importance because they mediate most of our physiological responses and act as therapeutic targets for a broad spectrum of diseases. In our review we focus on SMFS to characterize GPCRs embedded in their physiologically relevant membranes and exposed to physiologically relevant conditions. SMFS uses a molecularly sharp stylus to grasp the terminal end of a GPCR and to quickly unfold the receptor while recording interaction forces. The positional accuracy of SMFS localizes these interactions to structural segments of the GPCR whereas the sensitivity of SMFS enables their stabilizing interaction forces to be quantified. To further investigate the kinetic, energetic and mechanical properties of the structural segments, dynamic SMFS (DFS) probes their stability over a wide range of loading rates. These parameters provide insight into the energy landscape that provides information on the structural and functional properties of the GPCRs. Selected highlights exemplify the application of SMFS to characterize inter- and intramolecular interactions, which change the properties of GPCRs in relation to their functional state (e.g., ligand binding), diseased state (e.g., mutation), or lipid environment such as cholesterol.
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Affiliation(s)
- Michael Zocher
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland.
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18
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Whited AM, Park PSH. Atomic force microscopy: a multifaceted tool to study membrane proteins and their interactions with ligands. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:56-68. [PMID: 23603221 DOI: 10.1016/j.bbamem.2013.04.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/22/2013] [Accepted: 04/09/2013] [Indexed: 01/31/2023]
Abstract
Membrane proteins are embedded in lipid bilayers and facilitate the communication between the external environment and the interior of the cell. This communication is often mediated by the binding of ligands to the membrane protein. Understanding the nature of the interaction between a ligand and a membrane protein is required to both understand the mechanism of action of these proteins and for the development of novel pharmacological drugs. The highly hydrophobic nature of membrane proteins and the requirement of a lipid bilayer for native function have hampered the structural and molecular characterizations of these proteins under physiologically relevant conditions. Atomic force microscopy offers a solution to studying membrane proteins and their interactions with ligands under physiologically relevant conditions and can provide novel insights about the nature of these critical molecular interactions that facilitate cellular communication. In this review, we provide an overview of the atomic force microscopy technique and discuss its application in the study of a variety of questions related to the interaction between a membrane protein and a ligand. This article is part of a Special Issue entitled: Structural and biophysical characterization of membrane protein-ligand binding.
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Affiliation(s)
- Allison M Whited
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
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19
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Kawamura S, Gerstung M, Colozo AT, Helenius J, Maeda A, Beerenwinkel N, Park PSH, Müller DJ. Kinetic, energetic, and mechanical differences between dark-state rhodopsin and opsin. Structure 2013; 21:426-37. [PMID: 23434406 DOI: 10.1016/j.str.2013.01.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Revised: 01/05/2013] [Accepted: 01/15/2013] [Indexed: 11/20/2022]
Abstract
Rhodopsin, the photoreceptor pigment of the retina, initiates vision upon photon capture by its covalently linked chromophore 11-cis-retinal. In the absence of light, the chromophore serves as an inverse agonist locking the receptor in the inactive dark state. In the absence of chromophore, the apoprotein opsin shows low-level constitutive activity. Toward revealing insight into receptor properties controlled by the chromophore, we applied dynamic single-molecule force spectroscopy to quantify the kinetic, energetic, and mechanical differences between dark-state rhodopsin and opsin in native membranes from the retina of mice. Both rhodopsin and opsin are stabilized by ten structural segments. Compared to dark-state rhodopsin, the structural segments stabilizing opsin showed higher interaction strengths and mechanical rigidities and lower conformational variabilities, lifetimes, and free energies. These changes outline a common mechanism toward activating G-protein-coupled receptors. Additionally, we detected that opsin was more pliable and frequently stabilized alternate structural intermediates.
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Affiliation(s)
- Shiho Kawamura
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
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20
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Cholesterol increases kinetic, energetic, and mechanical stability of the human β2-adrenergic receptor. Proc Natl Acad Sci U S A 2012; 109:E3463-72. [PMID: 23151510 DOI: 10.1073/pnas.1210373109] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The steroid cholesterol is an essential component of eukaryotic membranes, and it functionally modulates membrane proteins, including G protein-coupled receptors. To reveal insight into how cholesterol modulates G protein-coupled receptors, we have used dynamic single-molecule force spectroscopy to quantify the mechanical strength and flexibility, conformational variability, and kinetic and energetic stability of structural segments stabilizing the human β(2)-adrenergic receptor (β(2)AR) in the absence and presence of the cholesterol analog cholesteryl hemisuccinate (CHS). CHS considerably increased the kinetic, energetic, and mechanical stability of almost every structural segment at sufficient magnitude to alter the structure and functional relationship of β(2)AR. One exception was the structural core segment of β(2)AR, which establishes multiple ligand binding sites, and its properties were not significantly influenced by CHS.
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21
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Trzaskowski B, Latek D, Yuan S, Ghoshdastider U, Debinski A, Filipek S. Action of molecular switches in GPCRs--theoretical and experimental studies. Curr Med Chem 2012; 19:1090-109. [PMID: 22300046 PMCID: PMC3343417 DOI: 10.2174/092986712799320556] [Citation(s) in RCA: 336] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 12/30/2011] [Accepted: 01/02/2012] [Indexed: 01/14/2023]
Abstract
G protein coupled receptors (GPCRs), also called 7TM receptors, form a huge superfamily of membrane proteins that, upon activation by extracellular agonists, pass the signal to the cell interior. Ligands can bind either to extracellular N-terminus and loops (e.g. glutamate receptors) or to the binding site within transmembrane helices (Rhodopsin-like family). They are all activated by agonists although a spontaneous auto-activation of an empty receptor can also be observed. Biochemical and crystallographic methods together with molecular dynamics simulations and other theoretical techniques provided models of the receptor activation based on the action of so-called "molecular switches" buried in the receptor structure. They are changed by agonists but also by inverse agonists evoking an ensemble of activation states leading toward different activation pathways. Switches discovered so far include the ionic lock switch, the 3-7 lock switch, the tyrosine toggle switch linked with the nPxxy motif in TM7, and the transmission switch. The latter one was proposed instead of the tryptophan rotamer toggle switch because no change of the rotamer was observed in structures of activated receptors. The global toggle switch suggested earlier consisting of a vertical rigid motion of TM6, seems also to be implausible based on the recent crystal structures of GPCRs with agonists. Theoretical and experimental methods (crystallography, NMR, specific spectroscopic methods like FRET/BRET but also single-molecule-force-spectroscopy) are currently used to study the effect of ligands on the receptor structure, location of stable structural segments/domains of GPCRs, and to answer the still open question on how ligands are binding: either via ensemble of conformational receptor states or rather via induced fit mechanisms. On the other hand the structural investigations of homoand heterodimers and higher oligomers revealed the mechanism of allosteric signal transmission and receptor activation that could lead to design highly effective and selective allosteric or ago-allosteric drugs.
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Affiliation(s)
- B Trzaskowski
- Faculty of Chemistry, University of Warsaw, ul. Pasteura 1, 02-093 Warsaw, Poland
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Zocher M, Fung JJ, Kobilka BK, Müller DJ. Ligand-specific interactions modulate kinetic, energetic, and mechanical properties of the human β2 adrenergic receptor. Structure 2012; 20:1391-402. [PMID: 22748765 DOI: 10.1016/j.str.2012.05.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 05/22/2012] [Accepted: 05/22/2012] [Indexed: 11/28/2022]
Abstract
G protein-coupled receptors (GPCRs) are a class of versatile proteins that transduce signals across membranes. Extracellular stimuli induce inter- and intramolecular interactions that change the functional state of GPCRs and activate intracellular messenger molecules. How these interactions are established and how they modulate the functional state of GPCRs remain to be understood. We used dynamic single-molecule force spectroscopy to investigate how ligand binding modulates the energy landscape of the human β2 adrenergic receptor (β2 AR). Five different ligands representing either agonists, inverse agonists or neutral antagonists established a complex network of interactions that tuned the kinetic, energetic, and mechanical properties of functionally important structural regions of β2 AR. These interactions were specific to the efficacy profile of the ligands investigated and suggest that the functional modulation of GPCRs follows structurally well-defined interaction patterns.
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Affiliation(s)
- Michael Zocher
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstr. 26, 4058 Basel, Switzerland
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Kawamura S, Colozo AT, Ge L, Müller DJ, Park PSH. Structural, energetic, and mechanical perturbations in rhodopsin mutant that causes congenital stationary night blindness. J Biol Chem 2012; 287:21826-35. [PMID: 22549882 DOI: 10.1074/jbc.m112.340182] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Several point mutations in rhodopsin cause retinal diseases including congenital stationary night blindness and retinitis pigmentosa. The mechanism by which a single amino acid residue substitution leads to dysfunction is poorly understood at the molecular level. A G90D point mutation in rhodopsin causes constitutive activity and leads to congenital stationary night blindness. It is unclear which perturbations the mutation introduces and how they can cause the receptor to be constitutively active. To reveal insight into these mechanisms, we characterized the perturbations introduced into dark state G90D rhodopsin from a transgenic mouse model expressing exclusively the mutant rhodopsin in rod photoreceptor cells. UV-visible absorbance spectroscopy revealed hydroxylamine accessibility to the chromophore-binding pocket of dark state G90D rhodopsin, which is not detected in dark state wild-type rhodopsin but is detected in light-activated wild-type rhodopsin. Single-molecule force spectroscopy suggested that the structural changes introduced by the mutation are small. Dynamic single-molecule force spectroscopy revealed that, compared with dark state wild-type rhodopsin, the G90D mutation decreased energetic stability and increased mechanical rigidity of most structural regions in the dark state mutant receptor. The observed structural, energetic, and mechanical changes in dark state G90D rhodopsin provide insights into the nature of perturbations caused by a pathological point mutation. Moreover, these changed properties observed for dark state G90D rhodopsin are consistent with properties expected for an active state.
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Affiliation(s)
- Shiho Kawamura
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland
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