1
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Marini C, Porro A, Rastetter A, Dalle C, Rivolta I, Bauer D, Oegema R, Nava C, Parrini E, Mei D, Mercer C, Dhamija R, Chambers C, Coubes C, Thévenon J, Kuentz P, Julia S, Pasquier L, Dubourg C, Carré W, Rosati A, Melani F, Pisano T, Giardino M, Innes AM, Alembik Y, Scheidecker S, Santos M, Figueiroa S, Garrido C, Fusco C, Frattini D, Spagnoli C, Binda A, Granata T, Ragona F, Freri E, Franceschetti S, Canafoglia L, Castellotti B, Gellera C, Milanesi R, Mancardi MM, Clark DR, Kok F, Helbig KL, Ichikawa S, Sadler L, Neupauerová J, Laššuthova P, Šterbová K, Laridon A, Brilstra E, Koeleman B, Lemke JR, Zara F, Striano P, Soblet J, Smits G, Deconinck N, Barbuti A, DiFrancesco D, LeGuern E, Guerrini R, Santoro B, Hamacher K, Thiel G, Moroni A, DiFrancesco JC, Depienne C. HCN1 mutation spectrum: from neonatal epileptic encephalopathy to benign generalized epilepsy and beyond. Brain 2019; 141:3160-3178. [PMID: 30351409 DOI: 10.1093/brain/awy263] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/09/2018] [Indexed: 12/15/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.
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Affiliation(s)
- Carla Marini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy.,EuroEPINOMICS RES Consortium
| | | | - Agnès Rastetter
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Carine Dalle
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Ilaria Rivolta
- School of Medicine and Surgery, University Milano-Bicocca, Monza, Italy
| | - Daniel Bauer
- Computational Biology and Simulation Group, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Renske Oegema
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Caroline Nava
- EuroEPINOMICS RES Consortium.,Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France.,AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Département de Génétique, Paris, France
| | - Elena Parrini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - Davide Mei
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - Catherine Mercer
- Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton, UK
| | - Radhika Dhamija
- Department of Clinical Genomics and Neurology, Mayo Clinic, Phoenix, AZ, USA
| | - Chelsea Chambers
- Department of Neurosciences, University of Virginia, Charlottesville, VA, USA
| | - Christine Coubes
- Département de Génétique Médicale, Maladies Rares et Médecine Personnalisée, Hôpital Arnaud de Villeneuve, Montpellier, France
| | - Julien Thévenon
- FHU-TRANSLAD, Université de Bourgogne/CHU Dijon and INSERM UMR 1231 GAD team, Genetics of Developmental Anomalies, Université de Bourgogne-Franche Comté, Dijon, France
| | - Paul Kuentz
- FHU-TRANSLAD, Université de Bourgogne/CHU Dijon and INSERM UMR 1231 GAD team, Genetics of Developmental Anomalies, Université de Bourgogne-Franche Comté, Dijon, France.,Génétique Biologique Histologie, CHRU de Besançon, Besançon, France
| | - Sophie Julia
- Service de génétique médicale, Pôle de biologie, CHU de Toulouse - Hôpital Purpan, Toulouse, France
| | - Laurent Pasquier
- Service de Génétique Clinique, Centre Référence Déficiences Intellectuelles de causes rares (CRDI), CHU Rennes, Rennes, France
| | - Christèle Dubourg
- Laboratoire de Génétique Moléculaire et Génomique, CHU de Rennes, Rennes, France
| | - Wilfrid Carré
- Laboratoire de Génétique Moléculaire et Génomique, CHU de Rennes, Rennes, France
| | - Anna Rosati
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - Federico Melani
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - Tiziana Pisano
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - Maria Giardino
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy
| | - A Micheil Innes
- Department of Medical Genetics and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Yves Alembik
- Laboratoires de génétique, Institut de génétique médicale d'Alsace, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Sophie Scheidecker
- Laboratoires de génétique, Institut de génétique médicale d'Alsace, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Manuela Santos
- Neuropediatric Department, Centro Hospitalar do Porto, Porto, Portugal
| | - Sonia Figueiroa
- Neuropediatric Department, Centro Hospitalar do Porto, Porto, Portugal
| | - Cristina Garrido
- Neuropediatric Department, Centro Hospitalar do Porto, Porto, Portugal
| | - Carlo Fusco
- Azienda Unità Sanitaria Locale - IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Daniele Frattini
- Azienda Unità Sanitaria Locale - IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Carlotta Spagnoli
- Azienda Unità Sanitaria Locale - IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Anna Binda
- School of Medicine and Surgery, University Milano-Bicocca, Monza, Italy
| | - Tiziana Granata
- Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | | | - Elena Freri
- Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | | | | | | | - Cinzia Gellera
- Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Raffaella Milanesi
- Department of Biosciences, The PaceLab, Università degli Studi di Milano, Milan, Italy
| | - Maria Margherita Mancardi
- Child Neuropsychiatry Unit, Department of Medical and Surgical Neurosciences and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genova, Italy
| | | | - Fernando Kok
- Mendelics Genomic Analysis, Sao Paulo, SP, Brazil
| | - Katherine L Helbig
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Shoji Ichikawa
- Department of Clinical Diagnostics, Ambry Genetics, Aliso Viejo, CA, USA
| | - Laurie Sadler
- Division of Genetics, Department of Pediatrics, Oishei Children's Hospital, Jacobs School of Medicine and Biomedical Sciences, University of Buffalo, State University of New York, Buffalo, NY, USA
| | - Jana Neupauerová
- Department of Child Neurology, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Petra Laššuthova
- Department of Child Neurology, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Katalin Šterbová
- EuroEPINOMICS RES Consortium.,Department of Child Neurology, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Annick Laridon
- Department of Neurology, Academic Center for Epileptology, Kempenhaeghe/Maastricht University Medical Center, Heeze, The Netherlands
| | - Eva Brilstra
- EuroEPINOMICS RES Consortium.,Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bobby Koeleman
- EuroEPINOMICS RES Consortium.,Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Johannes R Lemke
- EuroEPINOMICS RES Consortium.,Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | - Federico Zara
- Laboratory of Neurogenetics and Neuroscience, Institute G Gaslini, Genova, Italy
| | - Pasquale Striano
- EuroEPINOMICS RES Consortium.,Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 'G Gaslini' Institute, Genova, Italy
| | - Julie Soblet
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, ULB Center of Human Genetics, Université Libre de Bruxelles, Brussels, Belgium.,Department of Genetics, Hôpital Erasme ULB Center of Human Genetics, Université Libre de Bruxelles, Brussels, Belgium.,Interuniversity Institute of Bioinformatics in Brussels, Université Libre de Bruxelles, Brussels, Belgium
| | - Guillaume Smits
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, ULB Center of Human Genetics, Université Libre de Bruxelles, Brussels, Belgium.,Department of Genetics, Hôpital Erasme ULB Center of Human Genetics, Université Libre de Bruxelles, Brussels, Belgium.,Interuniversity Institute of Bioinformatics in Brussels, Université Libre de Bruxelles, Brussels, Belgium
| | - Nicolas Deconinck
- Department of Pediatric Neurology, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles, ULB, Brussels, Belgium
| | - Andrea Barbuti
- Department of Biosciences, The PaceLab, Università degli Studi di Milano, Milan, Italy
| | - Dario DiFrancesco
- Department of Biosciences, The PaceLab, Università degli Studi di Milano, Milan, Italy
| | - Eric LeGuern
- EuroEPINOMICS RES Consortium.,Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France.,AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Département de Génétique, Paris, France
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A Meyer Children's Hospital, University of Florence, Viale Pieraccini 24, Florence, Italy.,EuroEPINOMICS RES Consortium
| | - Bina Santoro
- Department of Neuroscience, Columbia University, New York, NY, USA
| | - Kay Hamacher
- Computational Biology and Simulation Group, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Gerhard Thiel
- Membrane Biophysics, Deparment of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences, University of Milan, Milan, Italy
| | - Jacopo C DiFrancesco
- Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.,Department of Neurology, San Gerardo Hospital, University Milano-Bicocca, Monza, Italy
| | - Christel Depienne
- EuroEPINOMICS RES Consortium.,Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France.,IGBMC, CNRS UMR 7104/INSERM U964/Université de Strasbourg, Illkirch, France.,Institute of Human Genetics, University Hospital Essen, University Duisburg-Essen, Essen, Germany
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2
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Hartel AJW, Shekar S, Ong P, Schroeder I, Thiel G, Shepard KL. High bandwidth approaches in nanopore and ion channel recordings - A tutorial review. Anal Chim Acta 2019; 1061:13-27. [PMID: 30926031 PMCID: PMC6860018 DOI: 10.1016/j.aca.2019.01.034] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 01/05/2019] [Indexed: 01/01/2023]
Abstract
Transport processes through ion-channel proteins, protein pores, or solid-state nanopores are traditionally recorded with commercial patch-clamp amplifiers. The bandwidth of these systems is typically limited to 10 kHz by signal-to-noise-ratio (SNR) considerations associated with these measurement platforms. At high bandwidth, the input-referred current noise in these systems dominates, determined by the input-referred voltage noise of the transimpedance amplifier applied across the capacitance at the input of the amplifier. This capacitance arises from several sources: the parasitic capacitance of the amplifier itself; the capacitance of the lipid bilayer harboring the ion channel protein (or the membrane used to form the solid-state nanopore); and the capacitance from the interconnections between the electronics and the membrane. Here, we review state-of-the-art applications of high-bandwidth conductance recordings of both ion channels and solid-state nanopores. These approaches involve tightly integrating measurement electronics fabricated in complementary metal-oxide semiconductors (CMOS) technology with lipid bilayer or solid-state membranes. SNR improvements associated with this tight integration push the limits of measurement bandwidths, in some cases in excess of 10 MHz. Recent case studies demonstrate the utility of these approaches for DNA sequencing and ion-channel recordings. In the latter case, studies with extended bandwidth have shown the potential for providing new insights into structure-function relations of these ion-channel proteins as the temporal resolutions of functional recordings matches time scales achievable with state-of-the-art molecular dynamics simulations.
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Affiliation(s)
- Andreas J W Hartel
- Bioelectronic Systems Laboratory, Department of Electrical Engineering, Columbia University, New York City, 10027, NY, USA.
| | - Siddharth Shekar
- Bioelectronic Systems Laboratory, Department of Electrical Engineering, Columbia University, New York City, 10027, NY, USA
| | - Peijie Ong
- Bioelectronic Systems Laboratory, Department of Electrical Engineering, Columbia University, New York City, 10027, NY, USA
| | - Indra Schroeder
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Kenneth L Shepard
- Bioelectronic Systems Laboratory, Department of Electrical Engineering, Columbia University, New York City, 10027, NY, USA.
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3
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Cao S, Konovalov KA, Unarta IC, Huang X. Recent Developments in Integral Equation Theory for Solvation to Treat Density Inhomogeneity at Solute–Solvent Interface. ADVANCED THEORY AND SIMULATIONS 2019. [DOI: 10.1002/adts.201900049] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Siqin Cao
- Department of Chemistrythe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
- Center of System Biology and Human HealthState Key Laboratory of Molecular Neuroscience, Hong Kong Branch Clear Water Bay Kowloon Hong Kong
| | - Kirill A. Konovalov
- Department of Chemistrythe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
- Center of System Biology and Human HealthState Key Laboratory of Molecular Neuroscience, Hong Kong Branch Clear Water Bay Kowloon Hong Kong
| | - Ilona Christy Unarta
- Center of System Biology and Human HealthState Key Laboratory of Molecular Neuroscience, Hong Kong Branch Clear Water Bay Kowloon Hong Kong
- Bioengineering Graduate Programthe Hong Kong University of Science and TechnologyHong Kong of Chinese National EngineeringResearch Center for Tissue Restoration and Reconstructionthe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
| | - Xuhui Huang
- Department of Chemistrythe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
- Center of System Biology and Human HealthState Key Laboratory of Molecular Neuroscience, Hong Kong Branch Clear Water Bay Kowloon Hong Kong
- Bioengineering Graduate Programthe Hong Kong University of Science and TechnologyHong Kong of Chinese National EngineeringResearch Center for Tissue Restoration and Reconstructionthe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
- HKUST‐Shenzhen Research Institute Hi‐Tech Park, Nanshan Shenzhen 518057 China
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4
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Rondelli V, Del Favero E, Brocca P, Fragneto G, Trapp M, Mauri L, Ciampa M, Romani G, Braun C, Winterstein L, Schroeder I, Thiel G, Moroni A, Cantu' L. Directional K+ channel insertion in a single phospholipid bilayer: Neutron reflectometry and electrophysiology in the joint exploration of a model membrane functional platform. Biochim Biophys Acta Gen Subj 2018; 1862:1742-1750. [DOI: 10.1016/j.bbagen.2018.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/27/2018] [Accepted: 05/07/2018] [Indexed: 01/05/2023]
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5
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Matter H, Güssregen S. Characterizing hydration sites in protein-ligand complexes towards the design of novel ligands. Bioorg Med Chem Lett 2018; 28:2343-2352. [PMID: 29880400 DOI: 10.1016/j.bmcl.2018.05.061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/28/2018] [Accepted: 05/30/2018] [Indexed: 11/18/2022]
Abstract
Water is an essential part of protein binding sites and mediates interactions to ligands. Its displacement by ligand parts affects the free binding energy of resulting protein-ligand complexes. Therefore the characterization of solvation properties is important for design. Of particular interest is the propensity of localized water to be favorably displaced by a ligand. This review discusses two popular computational approaches addressing these questions, namely WaterMap based on statistical mechanics analysis of MD simulations and 3D RISM based on integral equation theory of liquids. The theoretical background and recent applications in structure-based design will be presented.
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Affiliation(s)
- Hans Matter
- Sanofi-Aventis Deutschland GmbH, Integrated Drug Discovery (IDD), Synthetic Molecular Design, Building G838, Industriepark Höchst, 65926 Frankfurt am Main, Germany.
| | - Stefan Güssregen
- Sanofi-Aventis Deutschland GmbH, Integrated Drug Discovery (IDD), Synthetic Molecular Design, Building G838, Industriepark Höchst, 65926 Frankfurt am Main, Germany
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6
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Güssregen S, Matter H, Hessler G, Lionta E, Heil J, Kast SM. Thermodynamic Characterization of Hydration Sites from Integral Equation-Derived Free Energy Densities: Application to Protein Binding Sites and Ligand Series. J Chem Inf Model 2017; 57:1652-1666. [DOI: 10.1021/acs.jcim.6b00765] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stefan Güssregen
- R&D, IDD, Structural Design and Informatics, Sanofi-Aventis Deutschland GmbH, Industriepark Höchst, Building G877, 65926 Frankfurt am Main, Germany
| | - Hans Matter
- R&D, IDD, Structural Design and Informatics, Sanofi-Aventis Deutschland GmbH, Industriepark Höchst, Building G877, 65926 Frankfurt am Main, Germany
| | - Gerhard Hessler
- R&D, IDD, Structural Design and Informatics, Sanofi-Aventis Deutschland GmbH, Industriepark Höchst, Building G877, 65926 Frankfurt am Main, Germany
| | - Evanthia Lionta
- R&D, IDD, Structural Design and Informatics, Sanofi-Aventis Deutschland GmbH, Industriepark Höchst, Building G877, 65926 Frankfurt am Main, Germany
| | - Jochen Heil
- Physikalische
Chemie III, Technische Universität Dortmund, Otto-Hahn-Straße 4a, 44227 Dortmund, Germany
| | - Stefan M. Kast
- Physikalische
Chemie III, Technische Universität Dortmund, Otto-Hahn-Straße 4a, 44227 Dortmund, Germany
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7
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Baumeister D, Hertel B, Schroeder I, Gazzarrini S, Kast SM, Van Etten JL, Moroni A, Thiel G. Conversion of an instantaneous activating K + channel into a slow activating inward rectifier. FEBS Lett 2016; 591:295-303. [PMID: 27995608 DOI: 10.1002/1873-3468.12536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 12/27/2022]
Abstract
The miniature channel, Kcv, is a structural equivalent of the pore of all K+ channels. Here, we follow up on a previous observation that a largely voltage-insensitive channel can be converted into a slow activating inward rectifier after extending the outer transmembrane domain by one Ala. This gain of rectification can be rationalized by dynamic salt bridges at the cytosolic entrance to the channel; opening is favored by voltage-sensitive formation of salt bridges and counteracted by their disruption. Such latent voltage sensitivity in the pore could be relevant for the understanding of voltage gating in complex Kv channels.
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Affiliation(s)
- Dirk Baumeister
- Plant Membrane Biophysics, Technical University Darmstadt, Germany
| | - Brigitte Hertel
- Plant Membrane Biophysics, Technical University Darmstadt, Germany
| | - Indra Schroeder
- Plant Membrane Biophysics, Technical University Darmstadt, Germany
| | - Sabrina Gazzarrini
- Department of Biosciences and CNR IBF-Mi, Università degli Studi di Milano, Italy
| | - Stefan M Kast
- Physikalische Chemie III, Technische Universität Dortmund, Germany
| | - James L Van Etten
- Department of Plant Pathology, Nebraska Center for Virology, University of Nebraska Lincoln, NE, USA
| | - Anna Moroni
- Department of Biosciences and CNR IBF-Mi, Università degli Studi di Milano, Italy
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technical University Darmstadt, Germany
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8
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Schroeder I. How to resolve microsecond current fluctuations in single ion channels: the power of beta distributions. Channels (Austin) 2016; 9:262-80. [PMID: 26368656 DOI: 10.1080/19336950.2015.1083660] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A main ingredient for the understanding of structure/function correlates of ion channels is the quantitative description of single-channel gating and conductance. However, a wealth of information provided from fast current fluctuations beyond the temporal resolution of the recording system is often ignored, even though it is close to the time window accessible to molecular dynamics simulations. This kind of current fluctuations provide a special technical challenge, because individual opening/closing or blocking/unblocking events cannot be resolved, and the resulting averaging over undetected events decreases the single-channel current. Here, I briefly summarize the history of fast-current fluctuation analysis and focus on the so-called "beta distributions." This tool exploits characteristics of current fluctuation-induced excess noise on the current amplitude histograms to reconstruct the true single-channel current and kinetic parameters. A guideline for the analysis and recent applications demonstrate that a construction of theoretical beta distributions by Markov Model simulations offers maximum flexibility as compared to analytical solutions.
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Affiliation(s)
- Indra Schroeder
- a Plant Membrane Biophysics, Technical University of Darmstadt ; Darmstadt , Germany
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9
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Hoffgaard F, Kast S, Moroni A, Thiel G, Hamacher K. Tectonics of a K+ channel: The importance of the N-terminus for channel gating. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3197-204. [DOI: 10.1016/j.bbamem.2015.09.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 09/09/2015] [Accepted: 09/18/2015] [Indexed: 11/16/2022]
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10
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Ratkova EL, Palmer DS, Fedorov MV. Solvation thermodynamics of organic molecules by the molecular integral equation theory: approaching chemical accuracy. Chem Rev 2015; 115:6312-56. [PMID: 26073187 DOI: 10.1021/cr5000283] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Ekaterina L Ratkova
- †G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Akademicheskaya Street 1, Ivanovo 153045, Russia.,‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany
| | - David S Palmer
- ‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany.,§Department of Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, Scotland G1 1XL, United Kingdom
| | - Maxim V Fedorov
- ‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany.,∥Department of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, John Anderson Building, 107 Rottenrow East, Glasgow G4 0NG, United Kingdom
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11
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Abstract
The calculation of electrostatic solute-solvent interactions in 3D RISM ("three-dimensional reference interaction site model") integral equation theory is recast in a form that allows for a computational treatment analogous to the "particle-mesh Ewald" formalism as used for molecular simulations. In addition, relations that connect 3D RISM correlation functions and interaction potentials with thermodynamic quantities such as the chemical potential and average solute-solvent interaction energy are reformulated in a way that calculations of expensive real-space electrostatic terms on the 3D grid are completely avoided. These methodical enhancements allow for both, a significant speedup particularly for large solute systems and a smoother convergence of predicted thermodynamic quantities with respect to box size, as illustrated for several benchmark systems.
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Affiliation(s)
- Jochen Heil
- Physikalische Chemie III, Technische Universität Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Stefan M Kast
- Physikalische Chemie III, Technische Universität Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
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12
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Engineering a Ca⁺⁺⁺-sensitive (bio)sensor from the pore-module of a potassium channel. SENSORS 2015; 15:4913-24. [PMID: 25734643 PMCID: PMC4435187 DOI: 10.3390/s150304913] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 12/19/2014] [Accepted: 02/02/2015] [Indexed: 11/30/2022]
Abstract
Signals recorded at the cell membrane are meaningful indicators of the physiological vs. pathological state of a cell and will become useful diagnostic elements in nanomedicine. In this project we present a coherent strategy for the design and fabrication of a bio-nano-sensor that monitors changes in intracellular cell calcium concentration and allows an easy read out by converting the calcium signal into an electrical current in the range of microampere that can be easily measured by conventional cell electrophysiology apparatus.
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13
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Braun CJ, Baer T, Moroni A, Thiel G. Pseudo painting/air bubble technique for planar lipid bilayers. J Neurosci Methods 2014; 233:13-7. [DOI: 10.1016/j.jneumeth.2014.05.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 05/21/2014] [Accepted: 05/24/2014] [Indexed: 10/25/2022]
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14
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Romani G, Piotrowski A, Hillmer S, Gurnon J, Van Etten JL, Moroni A, Thiel G, Hertel B. A virus-encoded potassium ion channel is a structural protein in the chlorovirus Paramecium bursaria chlorella virus 1 virion. J Gen Virol 2013; 94:2549-2556. [PMID: 23918407 DOI: 10.1099/vir.0.055251-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most chloroviruses encode small K(+) channels, which are functional in electrophysiological assays. The experimental finding that initial steps in viral infection exhibit the same sensitivity to channel inhibitors as the viral K(+) channels has led to the hypothesis that the channels are structural proteins located in the internal membrane of the virus particles. This hypothesis was questioned recently because proteomic studies failed to detect the channel protein in virions of the prototype chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1). Here, we used a mAb raised against the functional K(+) channel from chlorovirus MA-1D to search for the viral K(+) channel in the virus particle. The results showed that the antibody was specific and bound to the tetrameric channel on the extracellular side. The antibody reacted in a virus-specific manner with protein extracts from chloroviruses that encoded channels similar to that from MA-1D. There was no cross-reactivity with chloroviruses that encoded more diverse channels or with a chlorovirus that lacked a K(+) channel gene. Together with electron microscopic imaging, which revealed labelling of individual virus particles with the channel antibody, these results establish that the viral particles contain an active K(+) channel, presumably located in the lipid membrane that surrounds the DNA in the mature virions.
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Affiliation(s)
- Giulia Romani
- Dipartimento di Bioscienze, Università degli Studi di Milano e Istituto di Biofisica, CNR, Milano, Italy
| | - Adrianna Piotrowski
- Membrane Biophysics Group, Department of Biology, Technical University Darmstadt, Germany
| | - Stefan Hillmer
- COS - Entwicklungsbiologie der Pflanzen, University of Heidelberg, Germany
| | - James Gurnon
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
| | - James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
| | - Anna Moroni
- Dipartimento di Bioscienze, Università degli Studi di Milano e Istituto di Biofisica, CNR, Milano, Italy
| | - Gerhard Thiel
- Membrane Biophysics Group, Department of Biology, Technical University Darmstadt, Germany
| | - Brigitte Hertel
- Membrane Biophysics Group, Department of Biology, Technical University Darmstadt, Germany
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15
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Braun CJ, Lachnit C, Becker P, Henkes LM, Arrigoni C, Kast SM, Moroni A, Thiel G, Schroeder I. Viral potassium channels as a robust model system for studies of membrane-protein interaction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1096-103. [PMID: 23791706 DOI: 10.1016/j.bbamem.2013.06.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 05/31/2013] [Accepted: 06/08/2013] [Indexed: 11/15/2022]
Abstract
The viral channel KcvNTS belongs to the smallest K(+) channels known so far. A monomer of a functional homotetramer contains only 82 amino acids. As a consequence of the small size the protein is almost fully submerged into the membrane. This suggests that the channel is presumably sensitive to its lipid environment. Here we perform a comparative analysis for the function of the channel protein embedded in three different membrane environments. 1. Single-channel currents of KcvNTS were recorded with the patch clamp method on the plasma membrane of HEK293 cells. 2. They were also measured after reconstitution of recombinant channel protein into classical planar lipid bilayers and 3. into horizontal bilayers derived from giant unilamellar vesicles (GUVs). The recombinant channel protein was either expressed and purified from Pichia pastoris or from a cell-free expression system; for the latter a new approach with nanolipoprotein particles was used. The data show that single-channel activity can be recorded under all experimental conditions. The main functional features of the channel like a large single-channel conductance (80pS), high open-probability (>50%) and the approximate duration of open and closed dwell times are maintained in all experimental systems. An apparent difference between the approaches was only observed with respect to the unitary conductance, which was ca. 35% lower in HEK293 cells than in the other systems. The reason for this might be explained by the fact that the channel is tagged by GFP when expressed in HEK293 cells. Collectively the data demonstrate that the small viral channel exhibits a robust function in different experimental systems. This justifies an extrapolation of functional data from these systems to the potential performance of the channel in the virus/host interaction. This article is part of a Special Issue entitled: Viral Membrane Proteins-Channels for Cellular Networking.
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Affiliation(s)
- Christian J Braun
- Membrane Biophysics, Technical University of Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Christine Lachnit
- Membrane Biophysics, Technical University of Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Patrick Becker
- Membrane Biophysics, Technical University of Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Leonhard M Henkes
- Physikalische Chemie III, Technische Universität Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Cristina Arrigoni
- Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milano, Italy
| | - Stefan M Kast
- Physikalische Chemie III, Technische Universität Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Anna Moroni
- Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milano, Italy; CNR-IBF, Via Celoria 26, 20133 Milano, Italy
| | - Gerhard Thiel
- Membrane Biophysics, Technical University of Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Indra Schroeder
- Membrane Biophysics, Technical University of Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.
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16
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Schroeder I, Gazzarrini S, Ferrara G, Thiel G, Hansen UP, Moroni A. Creation of a reactive oxygen species-insensitive Kcv channel. Biochemistry 2013; 52:3130-7. [PMID: 23578303 DOI: 10.1021/bi3016197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The current of the minimal viral K(+) channel Kcv(PCBV-1) heterologously expressed in Xenopus oocytes is strongly inhibited by reactive oxygen species (ROS) like H(2)O(2). Possible targets for the ROS effect are two cysteines (C53 and C79) and four methionines (M1, M15, M23, and M26). The C53A/C79A and M23L/M26L double mutations maintained the same ROS sensitivity as the wild type. However, M15L as a single mutant or in combination with C53A/C79A and/or M23L/M26L caused a complete loss of sensitivity to H(2)O(2). These results indicate a prominent role of M15 at the cytosolic end of the outer transmembrane helix for gating of Kcv(PCBV-1). Furthermore, even though the channel lacks a canonical voltage sensor, it exhibits a weak voltage sensitivity, resulting in a slight activation in the millisecond range after a voltage step to negative potentials. The M15L mutation inverts this kinetics into an inactivation, underlining the critical role of this residue for gating. The negative slope of the I-V curves of M15L is the same as in the wild type, indicating that the selectivity filter is not involved.
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Affiliation(s)
- Indra Schroeder
- Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milano, Italy.
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17
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Maffeo C, Bhattacharya S, Yoo J, Wells D, Aksimentiev A. Modeling and simulation of ion channels. Chem Rev 2012; 112:6250-84. [PMID: 23035940 PMCID: PMC3633640 DOI: 10.1021/cr3002609] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Christopher Maffeo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Swati Bhattacharya
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Jejoong Yoo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - David Wells
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
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18
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Gebhardt M, Henkes LM, Tayefeh S, Hertel B, Greiner T, Van Etten JL, Baumeister D, Cosentino C, Moroni A, Kast SM, Thiel G. Relevance of lysine snorkeling in the outer transmembrane domain of small viral potassium ion channels. Biochemistry 2012; 51:5571-9. [PMID: 22734656 DOI: 10.1021/bi3006016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Transmembrane domains (TMDs) are often flanked by Lys or Arg because they keep their aliphatic parts in the bilayer and their charged groups in the polar interface. Here we examine the relevance of this so-called "snorkeling" of a cationic amino acid, which is conserved in the outer TMD of small viral K(+) channels. Experimentally, snorkeling activity is not mandatory for Kcv(PBCV-1) because K29 can be replaced by most of the natural amino acids without any corruption of function. Two similar channels, Kcv(ATCV-1) and Kcv(MT325), lack a cytosolic N-terminus, and neutralization of their equivalent cationic amino acids inhibits their function. To understand the variable importance of the cationic amino acids, we reanalyzed molecular dynamics simulations of Kcv(PBCV-1) and N-terminally truncated mutants; the truncated mutants mimic Kcv(ATCV-1) and Kcv(MT325). Structures were analyzed with respect to membrane positioning in relation to the orientation of K29. The results indicate that the architecture of the protein (including the selectivity filter) is only weakly dependent on TMD length and protonation of K29. The penetration depth of Lys in a given protonation state is independent of the TMD architecture, which leads to a distortion of shorter proteins. The data imply that snorkeling can be important for K(+) channels; however, its significance depends on the architecture of the entire TMD. The observation that the most severe N-terminal truncation causes the outer TMD to move toward the cytosolic side suggests that snorkeling becomes more relevant if TMDs are not stabilized in the membrane by other domains.
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Affiliation(s)
- Manuela Gebhardt
- Botany Institute, Technische Universität Darmstadt, Darmstadt, Germany
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19
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Luchko T, Joung IS, Case DA. Integral Equation Theory of Biomolecules and Electrolytes. INNOVATIONS IN BIOMOLECULAR MODELING AND SIMULATIONS 2012. [DOI: 10.1039/9781849735049-00051] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The so-called three-dimensional version (3D-RISM) can be used to describe the interactions of solvent components (here we treat water and ions) with a chemical or biomolecular solute of arbitrary size and shape. Here we give an overview of the current status of such models, describing some aspects of “pure” electrolytes (water plus simple ions) and of ionophores, proteins and nucleic acids in the presence of water and salts. Here we focus primarily on interactions with water and dissolved salts; as a practical matter, the discussion is mostly limited to monovalent ions, since studies of divalent ions present many difficult problems that have not yet been addressed. This is not a comprehensive review, but covers a few recent examples that illustrate current issues.
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Affiliation(s)
- Tyler Luchko
- Department of Chemistry and Chemical Biology and BioMaPS Institute Rutgers University Piscataway NJ 08854, USA
| | - In Suk Joung
- Department of Chemistry and Chemical Biology and BioMaPS Institute Rutgers University Piscataway NJ 08854, USA
| | - David A. Case
- Department of Chemistry and Chemical Biology and BioMaPS Institute Rutgers University Piscataway NJ 08854, USA
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20
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Kast SM, Kloss T, Tayefeh S, Thiel G. A minimalist model for ion partitioning and competition in a K+ channel selectivity filter. ACTA ACUST UNITED AC 2012; 138:371-3. [PMID: 21875982 PMCID: PMC3171081 DOI: 10.1085/jgp.201110694] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Stefan M. Kast
- Physikalische Chemie III, Technische Universität Dortmund, D-44227 Dortmund, Germany
| | - Thomas Kloss
- Laboratoire de Physique et Modélisation des Milieux Condensés, Université Grenoble 1, Centre National de la Recherche Scientifique UMR 5493, F-38042 Grenoble, France
| | - Sascha Tayefeh
- Institut für Botanik, Technische Universität Darmstadt, D-64283 Darmstadt, Germany
| | - Gerhard Thiel
- Institut für Botanik, Technische Universität Darmstadt, D-64283 Darmstadt, Germany
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21
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Fischer WB, Wang YT, Schindler C, Chen CP. Mechanism of function of viral channel proteins and implications for drug development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:259-321. [PMID: 22364876 PMCID: PMC7149447 DOI: 10.1016/b978-0-12-394305-7.00006-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Viral channel-forming proteins comprise a class of viral proteins which, similar to their host companions, are made to alter electrochemical or substrate gradients across lipid membranes. These proteins are active during all stages of the cellular life cycle of viruses. An increasing number of proteins are identified as channel proteins, but the precise role in the viral life cycle is yet unknown for the majority of them. This review presents an overview about these proteins with an emphasis on those with available structural information. A concept is introduced which aligns the transmembrane domains of viral channel proteins with those of host channels and toxins to give insights into the mechanism of function of the viral proteins from potential sequence identities. A summary of to date investigations on drugs targeting these proteins is given and discussed in respect of their mode of action in vivo.
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Affiliation(s)
- Wolfgang B. Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Yi-Ting Wang
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Christina Schindler
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Chin-Pei Chen
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
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22
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Gebhardt M, Hoffgaard F, Hamacher K, Kast SM, Moroni A, Thiel G. Membrane anchoring and interaction between transmembrane domains are crucial for K+ channel function. J Biol Chem 2011; 286:11299-306. [PMID: 21310959 PMCID: PMC3064186 DOI: 10.1074/jbc.m110.211672] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Revised: 01/27/2011] [Indexed: 11/06/2022] Open
Abstract
The small viral channel Kcv is a Kir-like K(+) channel of only 94 amino acids. With this simple structure, the tetramer of Kcv represents the pore module of all complex K(+) channels. To examine the structural contribution of the transmembrane domains (TMDs) to channel function, we performed Ala scanning mutagenesis of the two domains and tested the functionality of the mutants in a yeast complementation assay. The data reveal, in combination with computational models, that the upper halves of both TMDs, which face toward the external medium, are rather rigid, whereas the inner parts are more flexible. The rigidity of the outer TMD is conferred by a number of essential aromatic amino acids that face the membrane and probably anchor this domain in the bilayer. The inner TMD is intimately connected with the rigid part of the outer TMD via π···π interactions between a pair of aromatic amino acids. This structural principle is conserved within the viral K(+) channels and also present in Kir2.2, implying a general importance of this architecture for K(+) channel function.
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Affiliation(s)
| | - Franziska Hoffgaard
- the Computational Biology Group, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Kay Hamacher
- the Computational Biology Group, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Stefan M. Kast
- the Physikalische Chemie III, Technische Universität Dortmund, 44227 Dortmund, Germany, and
| | - Anna Moroni
- the Department of Biology and Consiglio Nazionale delle Ricerche Istituto di Biofisica-Milano, Università degli Studi di Milano, 20122 Milan, Italy
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23
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Thiel G, Baumeister D, Schroeder I, Kast SM, Van Etten JL, Moroni A. Minimal art: or why small viral K(+) channels are good tools for understanding basic structure and function relations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:580-8. [PMID: 20417613 DOI: 10.1016/j.bbamem.2010.04.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Revised: 04/09/2010] [Accepted: 04/13/2010] [Indexed: 11/17/2022]
Abstract
Some algal viruses contain genes that encode proteins with the hallmarks of K(+) channels. One feature of these proteins is that they are less than 100 amino acids in size, which make them truly minimal for a K(+) channel protein. That is, they consist of only the pore module present in more complex K(+) channels. The combination of miniature size and the functional robustness of the viral K(+) channels make them ideal model systems for studying how K(+) channels work. Here we summarize recent structure/function correlates from these channels, which provide insight into functional properties such as gating, pharmacology and sorting in cells.
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Affiliation(s)
- Gerhard Thiel
- Institute of Botany, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.
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24
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Schmeer G, Maurer A. Development of thermodynamic properties of electrolyte solutions with the help of RISM-calculations at the Born–Oppenheimer level. Phys Chem Chem Phys 2010; 12:2407-17. [DOI: 10.1039/b917653e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Abenavoli A, DiFrancesco ML, Schroeder I, Epimashko S, Gazzarrini S, Hansen UP, Thiel G, Moroni A. Fast and slow gating are inherent properties of the pore module of the K+ channel Kcv. ACTA ACUST UNITED AC 2009; 134:219-29. [PMID: 19720961 PMCID: PMC2737228 DOI: 10.1085/jgp.200910266] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Kcv from the chlorella virus PBCV-1 is a viral protein that forms a tetrameric, functional K+ channel in heterologous systems. Kcv can serve as a model system to study and manipulate basic properties of the K+ channel pore because its minimalistic structure (94 amino acids) produces basic features of ion channels, such as selectivity, gating, and sensitivity to blockers. We present a characterization of Kcv properties at the single-channel level. In symmetric 100 mM K+, single-channel conductance is 114 ± 11 pS. Two different voltage-dependent mechanisms are responsible for the gating of Kcv. “Fast” gating, analyzed by β distributions, is responsible for the negative slope conductance in the single-channel current–voltage curve at extreme potentials, like in MaxiK potassium channels, and can be explained by depletion-aggravated instability of the filter region. The presence of a “slow” gating is revealed by the very low (in the order of 1–4%) mean open probability that is voltage dependent and underlies the time-dependent component of the macroscopic current.
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Affiliation(s)
- Alessandra Abenavoli
- Dipartimento di Biologia and Istituto di Biofisica-Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, 20133 Milan, Italy
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26
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Weil P, Hoffgaard F, Hamacher K. Estimating sufficient statistics in co-evolutionary analysis by mutual information. Comput Biol Chem 2009; 33:440-4. [PMID: 19910254 DOI: 10.1016/j.compbiolchem.2009.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 10/13/2009] [Accepted: 10/14/2009] [Indexed: 12/01/2022]
Abstract
Mutual information (MI) is a standard measure in information theory to observe and quantify correlated signals and events in both, empirical data sets and theoretical models. In the field of computational biology the MI turned out to be particularly useful in studies on co-evolutionary signals of sites within biomolecules. A key issue in the applicability of the MI is, however, a correct reference system or null model to understand finite-size effects in the underlying, finite data set. Although some bioinformatics studies exist with rigorous results for theoretical, well-designed random distributions, data from real-world proteins was never used to quantify the effect of finite-size samples. The impact of real-world statistics is, however, most relevant for researchers in all fields concerned with detecting evolutionary signals within biological sequences. We present results on such effects in finite-sized biological data sets and point to future research directions. We are most of all concerned with bacterial, ribosomal proteins as a prototypical example in molecular evolution. We compare to previous published suggestions, give an empirical formula, and propose a protocol to guide future research projects.
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Affiliation(s)
- Philipp Weil
- Theoretical Biology and Bioinformatics, Institute of Microbiology and Genetics, Department of Biology, TU Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany.
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27
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Patargias G, Barke T, Watts A, Fischer WB. Model generation of viral channel forming 2B protein bundles from polio and coxsackie viruses. Mol Membr Biol 2009; 26:309-20. [PMID: 19707940 DOI: 10.1080/09687680903164101] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
2B is a 99 amino acid membrane protein encoded by enteroviruses such as polio and coxsackie viruses with two transmembrane domains. The protein is found to make membranes of infected cells permeable. Using a computational approach which positions the models and assesses stability by molecular dynamics (MD) simulations a putative tetrameric bundle model of 2B is generated. The bundles show a pore lining motif of three lysines followed by a serine. The bundle is discussed in terms of different possible orientations of the helices in the membrane and the consequences this has on the in vivo activity of 2B.
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Affiliation(s)
- George Patargias
- Biomembrane Structure Unit, Department of Biochemistry, Oxford University, Oxford, UK
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28
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Using a five-state model for fitting amplitude histograms from MaxiK channels: beta-distributions reveal more than expected. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:1101-14. [PMID: 19626320 DOI: 10.1007/s00249-009-0515-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 06/25/2009] [Accepted: 06/29/2009] [Indexed: 12/19/2022]
Abstract
Fast gating of ion channels with rate constants higher than the corner frequency of the recording set-up can be evaluated by fitting so-called beta distributions to measured amplitude histograms. Up to now, this was preferentially done for O-C Markov sub-models with one open and one closed state. Here, a fit of the amplitude histograms from MaxiK (BK) single-channel records was achieved with a five-state model with two open and three closed states including three open-close transitions with rate constants higher than the corner frequency (20 kHz) of the inevitable low-pass filter of the recording system. The numerical values of the rate constants of these transitions enabled a nearly one-to-one relationship between typical regions of the histograms and the reactions in the Markov model. These characteristic features are the width of the peak at the apparent single-channel current, the side slopes at the open and at the closed peak, and the depth of the valley between the two peaks. However, the simplex routine alone was incapable of finding the solution but could do so if guided by hand along a suggested strategy.
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29
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Interference of shot noise of open-channel current with analysis of fast gating: patchers do not (Yet) have to care. J Membr Biol 2009; 229:153-63. [PMID: 19551329 DOI: 10.1007/s00232-009-9183-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 06/02/2009] [Indexed: 12/25/2022]
Abstract
Microsecond gating of ion channels can be evaluated by fitting beta distributions to amplitude histograms of measured time series. The shape of these histograms is determined not only by the rate constants of the gating process (in relation to the filter frequency) but also by baseline noise and shot noise, resulting from the stochastic nature of ion flow. Under normal temporal resolution, the small shot noise can be ignored. This simplification may no longer be legitimate when rate constants reach the range above 1 mus(-1). Here, the influence of shot noise is studied by means of simulated time series for several values of single-channel current of the fully open state and baseline noise. Under realistic optimal conditions (16 pA current, 1 pA noise, 50 kHz bandwidth), ignoring the shot noise leads to an underestimation of the rate constants above 1 mus(-1) by a factor of about 2.5. However, in that range, the scatter of the evaluated rate constants is at least of the same magnitude, obscuring the systematic error. The incorporation of shot noise into the analysis will become more important when amplifiers with significantly reduced noise become available.
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30
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Grunwald I, Rischka K, Kast SM, Scheibel T, Bargel H. Mimicking biopolymers on a molecular scale: nano(bio)technology based on engineered proteins. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:1727-1747. [PMID: 19376768 DOI: 10.1098/rsta.2009.0012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Proteins are ubiquitous biopolymers that adopt distinct three-dimensional structures and fulfil a multitude of elementary functions in organisms. Recent systematic studies in molecular biology and biotechnology have improved the understanding of basic functional and architectural principles of proteins, making them attractive candidates as concept generators for technological development in material science, particularly in biomedicine and nano(bio)technology. This paper highlights the potential of molecular biomimetics in mimicking high-performance proteins and provides concepts for applications in four case studies, i.e. spider silk, antifreeze proteins, blue mussel adhesive proteins and viral ion channels.
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Affiliation(s)
- Ingo Grunwald
- Department of Adhesive Bonding Technology and Surfaces, Fraunhofer Institute for Manufacturing Technology and Applied Materials Research (IFAM)28359 Bremen, Germany
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Salt bridges in the miniature viral channel Kcv are important for function. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:1057-68. [PMID: 19390850 DOI: 10.1007/s00249-009-0451-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 03/14/2009] [Accepted: 03/31/2009] [Indexed: 10/20/2022]
Abstract
The viral potassium channel Kcv comprises only 94 amino acids, which represent the pore module of more complex K(+) channels. As for Kir-type channels, Kcv also has a short N-terminal helix exposed to the cytoplasm, upstream of the first transmembrane domain. Here we show that this helix is relevant for Kcv function. The presence of charged amino acids, which form dynamic inter- and intra-subunit salt bridges is crucial. Electrophysiological measurements, yeast rescue experiments and molecular dynamics simulations show that mutants in which the critical salt bridge formation is impaired have no or reduced channel activity. We conclude that these salt bridges destabilise the complexation of K(+) ions by negative charges on the inner transmembrane domain at the entrance into the cavity. This feature facilitates a continuous and coordinated transfer of ions between the cavity and the cytoplasm for channels without the canonical bundle crossing.
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Tayefeh S, Kloss T, Kreim M, Gebhardt M, Baumeister D, Hertel B, Richter C, Schwalbe H, Moroni A, Thiel G, Kast SM. Model development for the viral Kcv potassium channel. Biophys J 2009; 96:485-98. [PMID: 19167299 DOI: 10.1016/j.bpj.2008.09.050] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Accepted: 09/29/2008] [Indexed: 11/24/2022] Open
Abstract
A computational model for the open state of the short viral Kcv potassium channel was created and tested based on homology modeling and extensive molecular-dynamics simulation in a membrane environment. Particular attention was paid to the structure of the highly flexible N-terminal region and to the protonation state of membrane-exposed lysine residues. Data from various experimental sources, NMR spectroscopy, and electrophysiology, as well as results from three-dimensional reference interaction site model integral equation theory were taken into account to select the most reasonable model among possible variants. The final model exhibits spontaneous ion transitions across the complete pore, with and without application of an external field. The nonequilibrium transport events could be induced reproducibly without abnormally large driving potential and without the need to place ions artificially at certain key positions along the transition path. The transport mechanism through the filter region corresponds to the classic view of single-file motion, which in our case is coupled to frequent exchange of ions between the innermost filter position and the cavity.
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Affiliation(s)
- Sascha Tayefeh
- Eduard Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Darmstadt, Germany
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Wilson WH, Van Etten JL, Allen MJ. The Phycodnaviridae: the story of how tiny giants rule the world. Curr Top Microbiol Immunol 2009; 328:1-42. [PMID: 19216434 DOI: 10.1007/978-3-540-68618-7_1] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The family Phycodnaviridae encompasses a diverse and rapidly expanding collection of large icosahedral, dsDNA viruses that infect algae. These lytic and lysogenic viruses have genomes ranging from 160 to 560 kb. The family consists of six genera based initially on host range and supported by sequence comparisons. The family is monophyletic with branches for each genus, but the phycodnaviruses have evolutionary roots that connect them with several other families of large DNA viruses, referred to as the nucleocytoplasmic large DNA viruses (NCLDV). The phycodnaviruses have diverse genome structures, some with large regions of noncoding sequence and others with regions of ssDNA. The genomes of members in three genera in the Phycodnaviridae have been sequenced. The genome analyses have revealed more than 1000 unique genes, with only 14 homologous genes in common among the three genera of phycodnaviruses sequenced to date. Thus, their gene diversity far exceeds the number of so-called core genes. Not much is known about the replication of these viruses, but the consequences of these infections on phytoplankton have global affects, including influencing geochemical cycling and weather patterns.
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Affiliation(s)
- W H Wilson
- Bigelow Laboratory for Ocean Sciences, 180 McKown Point, P.O. Box 475, West Boothbay Harbor, ME 04575-0475, USA.
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Kloss T, Kast SM. Treatment of charged solutes in three-dimensional integral equation theory. J Chem Phys 2008; 128:134505. [DOI: 10.1063/1.2841967] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Chlorella viruses evoke a rapid release of K+ from host cells during the early phase of infection. Virology 2008; 372:340-8. [DOI: 10.1016/j.virol.2007.10.024] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 09/30/2007] [Accepted: 10/24/2007] [Indexed: 11/18/2022]
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Schroeder I, Hansen UP. Saturation and microsecond gating of current indicate depletion-induced instability of the MaxiK selectivity filter. ACTA ACUST UNITED AC 2007; 130:83-97. [PMID: 17591987 PMCID: PMC2154363 DOI: 10.1085/jgp.200709802] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Patch clamp experiments on single MaxiK channels expressed in HEK293 cells were performed with a high temporal resolution (50-kHz filter) in symmetrical solutions with 50, 150, or 400 mM KCl and 2.5 mM CaCl(2) and 2.5 mM MgCl(2). At membrane potentials >+100 mV, the single-channel current showed a negative slope resistance, concomitantly with a flickery block, which was not influenced by Ca(2+) or Mg(2+). The analysis of the amplitude histograms by beta distributions revealed that current in this voltage range was reduced by two effects: rate limitation at the cytosolic side of the pore and gating with rate constants 10-20-fold higher than the cutoff frequency of the filter (i.e., dwell times in the microsecond range). The data were analyzed in terms of a model that postulates a coupling between both effects; if the voltage over the selectivity filter withdraws ions from the cavity at a higher rate than that of refilling from the cytosol, the selectivity filter becomes instable because of ion depletion, and current is interrupted by the resulting flickering. The fit of the IV curves revealed a characteristic voltage of 35 mV. In contrast, the voltage dependence of the gating factor R, i.e., the ratio between true and apparent single-channel current, could be fitted by exponentials with a characteristic voltage of 60 mV, suggesting that only part of the transmembrane potential is felt by the flux through the selectivity filter.
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Affiliation(s)
- Indra Schroeder
- Department of Structural Biology, University of Kiel, 24098 Kiel, Germany
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