1
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Asrani P, Seebohm G, Stoll R. Potassium viroporins as model systems for understanding eukaryotic ion channel behaviour. Virus Res 2022; 320:198903. [PMID: 36037849 DOI: 10.1016/j.virusres.2022.198903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 11/29/2022]
Abstract
Ion channels are membrane proteins essential for a plethora of cellular functions including maintaining cell shape, ion homeostasis, cardiac rhythm and action potential in neurons. The complexity and often extensive structure of eukaryotic membrane proteins makes it difficult to understand their basic biological regulation. Therefore, this article suggests, viroporins - the miniature versions of eukaryotic protein homologs from viruses - might serve as model systems to provide insights into behaviour of eukaryotic ion channels in general. The structural requirements for correct assembly of the channel along with the basic functional properties of a K+ channel exist in the minimal design of the viral K+ channels from two viruses, Chlorella virus (Kcv) and Ectocarpus siliculosus virus (Kesv). These small viral proteins readily assemble into tetramers and they sort in cells to distinct target membranes. When these viruses-encoded channels are expressed into the mammalian cells, they utilise their protein machinery and hence can serve as excellent tools to study the cells protein sorting machinery. This combination of small size and robust function makes viral K+ channels a valuable model system for detection of basic structure-function correlations. It is believed that molecular and physiochemical analyses of these viroporins may serve as basis for the development of inhibitors or modulators to ion channel activity for targeting ion channel diseases - so called channelopathies. Therefore, it may provide a potential different scope for molecular pharmacology studies aiming at novel and innovative therapeutics associated with channel related diseases. This article reviews the structural and functional properties of Kcv and Kesv upon expression in mammalian cells and Xenopus oocytes. The mechanisms behind differential protein sorting in Kcv and Kesv are also thoroughly discussed.
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Affiliation(s)
- Purva Asrani
- Biomolecular Spectroscopy and RUBiospec|NMR, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, Bochum D-44780, Germany
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster D-48149, Germany
| | - Raphael Stoll
- Biomolecular Spectroscopy and RUBiospec|NMR, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, Bochum D-44780, Germany.
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2
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Rauh O, Opper J, Sturm M, Drexler N, Scheub DD, Hansen UP, Thiel G, Schroeder I. Role of ion distribution and energy barriers for concerted motion of subunits in selectivity filter gating of a K+ channel. J Mol Biol 2022; 434:167522. [DOI: 10.1016/j.jmb.2022.167522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/04/2022] [Accepted: 02/28/2022] [Indexed: 11/25/2022]
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3
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Gabriel TS, Hansen UP, Urban M, Drexler N, Winterstein T, Rauh O, Thiel G, Kast SM, Schroeder I. Asymmetric Interplay Between K + and Blocker and Atomistic Parameters From Physiological Experiments Quantify K + Channel Blocker Release. Front Physiol 2021; 12:737834. [PMID: 34777005 PMCID: PMC8586521 DOI: 10.3389/fphys.2021.737834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 10/04/2021] [Indexed: 11/23/2022] Open
Abstract
Modulating the activity of ion channels by blockers yields information on both the mode of drug action and on the biophysics of ion transport. Here we investigate the interplay between ions in the selectivity filter (SF) of K+ channels and the release kinetics of the blocker tetrapropylammonium in the model channel KcvNTS. A quantitative expression calculates blocker release rate constants directly from voltage-dependent ion occupation probabilities in the SF. The latter are obtained by a kinetic model of single-channel currents recorded in the absence of the blocker. The resulting model contains only two adjustable parameters of ion-blocker interaction and holds for both symmetric and asymmetric ionic conditions. This data-derived model is corroborated by 3D reference interaction site model (3D RISM) calculations on several model systems, which show that the K+ occupation probability is unaffected by the blocker, a direct consequence of the strength of the ion-carbonyl attraction in the SF, independent of the specific protein background. Hence, KcvNTS channel blocker release kinetics can be reduced to a small number of system-specific parameters. The pore-independent asymmetric interplay between K+ and blocker ions potentially allows for generalizing these results to similar potassium channels.
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Affiliation(s)
- Tobias S Gabriel
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Ulf-Peter Hansen
- Department of Structural Biology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Martin Urban
- Physikalische Chemie III, Technische Universita̋t Dortmund, Dortmund, Germany
| | - Nils Drexler
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany
| | - Tobias Winterstein
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Oliver Rauh
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Stefan M Kast
- Physikalische Chemie III, Technische Universita̋t Dortmund, Dortmund, Germany
| | - Indra Schroeder
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany.,Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany
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4
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Genetic Diversity of Potassium Ion Channel Proteins Encoded by Chloroviruses That Infect Chlorella heliozoae. Viruses 2020; 12:v12060678. [PMID: 32585987 PMCID: PMC7354518 DOI: 10.3390/v12060678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 12/17/2022] Open
Abstract
Chloroviruses are large, plaque-forming, dsDNA viruses that infect chlorella-like green algae that live in a symbiotic relationship with protists. Chloroviruses have genomes from 290 to 370 kb, and they encode as many as 400 proteins. One interesting feature of chloroviruses is that they encode a potassium ion (K+) channel protein named Kcv. The Kcv protein encoded by SAG chlorovirus ATCV-1 is one of the smallest known functional K+ channel proteins consisting of 82 amino acids. The KcvATCV-1 protein has similarities to the family of two transmembrane domain K+ channel proteins; it consists of two transmembrane α-helixes with a pore region in the middle, making it an ideal model for studying K+ channels. To assess their genetic diversity, kcv genes were sequenced from 103 geographically distinct SAG chlorovirus isolates. Of the 103 kcv genes, there were 42 unique DNA sequences that translated into 26 new Kcv channels. The new predicted Kcv proteins differed from KcvATCV-1 by 1 to 55 amino acids. The most conserved region of the Kcv protein was the filter, the turret and the pore helix were fairly well conserved, and the outer and the inner transmembrane domains of the protein were the most variable. Two of the new predicted channels were shown to be functional K+ channels.
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5
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Van Etten JL, Agarkova IV, Dunigan DD. Chloroviruses. Viruses 2019; 12:E20. [PMID: 31878033 PMCID: PMC7019647 DOI: 10.3390/v12010020] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/13/2019] [Accepted: 12/15/2019] [Indexed: 12/20/2022] Open
Abstract
Chloroviruses are large dsDNA, plaque-forming viruses that infect certain chlorella-like green algae; the algae are normally mutualistic endosymbionts of protists and metazoans and are often referred to as zoochlorellae. The viruses are ubiquitous in inland aqueous environments throughout the world and occasionally single types reach titers of thousands of plaque-forming units per ml of native water. The viruses are icosahedral in shape with a spike structure located at one of the vertices. They contain an internal membrane that is required for infectivity. The viral genomes are 290 to 370 kb in size, which encode up to 16 tRNAs and 330 to ~415 proteins, including many not previously seen in viruses. Examples include genes encoding DNA restriction and modification enzymes, hyaluronan and chitin biosynthetic enzymes, polyamine biosynthetic enzymes, ion channel and transport proteins, and enzymes involved in the glycan synthesis of the virus major capsid glycoproteins. The proteins encoded by many of these viruses are often the smallest or among the smallest proteins of their class. Consequently, some of the viral proteins are the subject of intensive biochemical and structural investigation.
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Affiliation(s)
- James L. Van Etten
- Department of Plant Pathology, Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE 68583-0900, USA; (I.V.A.); (D.D.D.)
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6
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Maeda SI, Aoba R, Nishino Y, Omata T. A Novel Bacterial Nitrate Transporter Composed of Small Transmembrane Proteins. PLANT & CELL PHYSIOLOGY 2019; 60:2180-2192. [PMID: 31198965 DOI: 10.1093/pcp/pcz112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Accepted: 05/27/2019] [Indexed: 06/09/2023]
Abstract
A putative silent gene of the freshwater cyanobacterium Synechococcus elongatus strain PCC 7942, encoding a small protein with two transmembrane helices, was named nrtS, since its overexpression from an inducible promoter conferred nitrate uptake activity on the nitrate transport-less NA4 mutant of S. elongatus. Homologs of nrtS, encoding proteins of 67-118 amino acid residues, are present in a limited number of eubacteria including mostly cyanobacteria and proteobacteria, but some others, e.g. the actinobacteria of the Mycobacterium tuberculosis complex, also have the gene. When expressed in NA4, the nrtS homolog of the γ-proteobacterium Marinomonas mediterranea took up nitrate with higher affinity for the substrate as compared with the S. elongatus NrtS (Km of 0.49 mM vs. 2.5 mM). Among the 61 bacterial species carrying the nrtS homolog, the marine cyanobacterium Synechococcus sp. strain PCC 7002 is unique in having two nrtS genes (nrtS1 and nrtS2) located in tandem on the chromosome. Coexpression of the two genes in NA4 resulted in nitrate uptake with a Km (NO3-) of 0.15 mM, while expression of either of the two resulted in low-affinity nitrate uptake activity with Km values of >3 mM, indicating that NrtS1 and NrtS2 form a heteromeric transporter complex. The heteromeric transporter was shown to transport nitrite as well. A Synechococcus sp. strain PCC 7002 mutant defective in the nitrate transporter (NrtP) showed a residual activity of nitrate uptake, which was ascribed to the NrtS proteins. Blue-native PAGE and immunoblotting analysis suggested a hexameric structure for the NrtS proteins.
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Affiliation(s)
- Shin-Ichi Maeda
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Risa Aoba
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Yuma Nishino
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Tatsuo Omata
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
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7
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Schönrock M, Thiel G, Laube B. Coupling of a viral K +-channel with a glutamate-binding-domain highlights the modular design of ionotropic glutamate-receptors. Commun Biol 2019; 2:75. [PMID: 30820470 PMCID: PMC6385376 DOI: 10.1038/s42003-019-0320-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 01/22/2019] [Indexed: 01/12/2023] Open
Abstract
Ionotropic glutamate receptors (iGluRs) mediate excitatory neuronal signaling in the mammalian CNS. These receptors are critically involved in diverse physiological processes; including learning and memory formation, as well as neuronal damage associated with neurological diseases. Based on partial sequence and structural similarities, these complex cation-permeable iGluRs are thought to descend from simple bacterial proteins emerging from a fusion of a substrate binding protein (SBP) and an inverted potassium (K+)-channel. Here, we fuse the pore module of the viral K+-channel KcvATCV-1 to the isolated glutamate-binding domain of the mammalian iGluR subunit GluA1 which is structural homolog to SBPs. The resulting chimera (GluATCV*) is functional and displays the ligand recognition characteristics of GluA1 and the K+-selectivity of KcvATCV-1. These results are consistent with a conserved activation mechanism between a glutamate-binding domain and the pore-module of a K+-channel and support the expected phylogenetic link between the two protein families.
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Affiliation(s)
- Michael Schönrock
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Gerhard Thiel
- Department of Biology, Plant Membrane Biophysics, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Bodo Laube
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, 64289, Darmstadt, Germany.
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8
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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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9
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Rauh O, Hansen UP, Scheub DD, Thiel G, Schroeder I. Site-specific ion occupation in the selectivity filter causes voltage-dependent gating in a viral K + channel. Sci Rep 2018; 8:10406. [PMID: 29991721 PMCID: PMC6039446 DOI: 10.1038/s41598-018-28751-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 06/28/2018] [Indexed: 12/24/2022] Open
Abstract
Many potassium channels show voltage-dependent gating without a dedicated voltage sensor domain. This is not fully understood yet, but often explained by voltage-induced changes of ion occupation in the five distinct K+ binding sites in the selectivity filter. To better understand this mechanism of filter gating we measured the single-channel current and the rate constant of sub-millisecond channel closure of the viral K+ channel KcvNTS for a wide range of voltages and symmetric and asymmetric K+ concentrations in planar lipid membranes. A model-based analysis employed a global fit of all experimental data, i.e., using a common set of parameters for current and channel closure under all conditions. Three different established models of ion permeation and various relationships between ion occupation and gating were tested. Only one of the models described the data adequately. It revealed that the most extracellular binding site (S0) in the selectivity filter functions as the voltage sensor for the rate constant of channel closure. The ion occupation outside of S0 modulates its dependence on K+ concentration. The analysis uncovers an important role of changes in protein flexibility in mediating the effect from the sensor to the gate.
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Affiliation(s)
- O Rauh
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - U P Hansen
- Department of Structural Biology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - D D Scheub
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - G Thiel
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - I Schroeder
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany.
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10
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Xiong W, Wang P, Yan T, Cao B, Xu J, Liu D, Luo M. The rice "fruit-weight 2.2-like" gene family member OsFWL4 is involved in the translocation of cadmium from roots to shoots. PLANTA 2018; 247:1247-1260. [PMID: 29453663 DOI: 10.1007/s00425-018-2859-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 01/31/2018] [Indexed: 06/08/2023]
Abstract
Heterogeneous expression of the rice genes "fruit-weight 2.2-like" (OsFWL) affects Cd resistance in yeast, and OsFWL4 mediates the translocation of Cd from roots to shoots. Cadmium (Cd) induces chronic and toxic effects in humans. In a previous study (Xu et al. in Planta 238:643-655, 2013), we cloned the rice genes, designated OsFWL1-8, homologous to the tomato fruit-weight 2.2. Here, we show that expression of genes OsFWL3-7 in yeast confers resistance to Cd. The Cd contents of OsFWL3-, -4-, -6- and -7-transformed Cd(II)-sensitive yeast mutant ycf1 cells were strongly decreased compared with those of empty vector, with the strongest resistance to Cd observed in cells expressing OsFWL4. Evaluation of truncated and site-directed mutation derivatives revealed that the CCXXG motifs near the second transmembrane region of OsFWL4 are involved in Cd resistance in yeast. Real-time PCR analysis showed that OsFWL4 expression was induced by CdCl2 stress in rice seedlings. Compared with WT plants, the Cd contents in the shoots of RNAi mediated OsFWL4 knockdown plants were significantly decreased, and Cd translocation from roots to shoots was reduced. According to bimolecular fluorescence complementation, yeast two-hybrid and Western-blotting assays, the OsFWL4 protein forms homo-oligomers. These results suggest that OsFWL4 might act directly as a transporter and is involved in the translocation of Cd from roots to shoots in rice.
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Affiliation(s)
- Wentao Xiong
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Peng Wang
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Tianze Yan
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Baobao Cao
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Jun Xu
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Defang Liu
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Meizhong Luo
- National Key Laboratory of Crop Genetic Improvement and College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
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11
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Winterstein LM, Kukovetz K, Rauh O, Turman DL, Braun C, Moroni A, Schroeder I, Thiel G. Reconstitution and functional characterization of ion channels from nanodiscs in lipid bilayers. J Gen Physiol 2018; 150:637-646. [PMID: 29487088 PMCID: PMC5881443 DOI: 10.1085/jgp.201711904] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/20/2017] [Accepted: 01/30/2018] [Indexed: 11/20/2022] Open
Abstract
Recent studies have shown that membrane proteins can be efficiently synthesized in vitro before spontaneously inserting into soluble nanoscale lipid bilayers called nanodiscs (NDs). In this paper, we present experimental details that allow a combination of in vitro translation of ion channels into commercially available NDs followed by their direct reconstitution from these nanobilayers into standard bilayer setups for electrophysiological characterization. We present data showing that two model K+ channels, Kcv and KcsA, as well as a recently discovered dual-topology F- channel, Fluc, can be reliably reconstituted from different types of NDs into bilayers without contamination from the in vitro translation cocktail. The functional properties of Kcv and KcsA were characterized electrophysiologically and exhibited sensitivity to the lipid composition of the target DPhPC bilayer, suggesting that the channel proteins were fully exposed to the target membrane and were no longer surrounded by the lipid/protein scaffold. The single-channel properties of the three tested channels are compatible with studies from recordings of the same proteins in other expression systems. Altogether, the data show that synthesis of ion channels into NDs and their subsequent reconstitution into conventional bilayers provide a fast and reliable method for functional analysis of ion channels.
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Affiliation(s)
| | - Kerri Kukovetz
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Oliver Rauh
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Daniel L Turman
- Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA
| | - Christian Braun
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences and Consiglio Nazionale delle Ricerche - Istituto di Biofisica, Università degli Studi di Milano, Milano, Italy
| | - Indra Schroeder
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany
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Rauh O, Hansen U, Mach S, Hartel AJ, Shepard KL, Thiel G, Schroeder I. Extended beta distributions open the access to fast gating in bilayer experiments-assigning the voltage-dependent gating to the selectivity filter. FEBS Lett 2017; 591:3850-3860. [PMID: 29106736 PMCID: PMC5747313 DOI: 10.1002/1873-3468.12898] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 10/17/2017] [Accepted: 10/27/2017] [Indexed: 01/02/2023]
Abstract
Lipid bilayers provide many benefits for ion channel recordings, such as control of membrane composition and transport molecules. However, they suffer from high membrane capacitance limiting the bandwidth and impeding analysis of fast gating. This can be overcome by fitting the deviations of the open-channel noise from the baseline noise by extended beta distributions. We demonstrate this analysis step-by-step by applying it to the example of viral K+ channels (Kcv), from the choice of the gating model through the fitting process, validation of the results, and what kinds of results can be obtained. These voltage sensor-less channels show profoundly voltage-dependent gating with dwell times in the closed state of about 50 μs. Mutations assign it to the selectivity filter.
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Affiliation(s)
- Oliver Rauh
- Plant Membrane BiophysicsTechnische Universität DarmstadtGermany
| | - Ulf‐Peter Hansen
- Department of Structural BiologyChristian‐Albrechts‐University of KielGermany
| | - Sebastian Mach
- Plant Membrane BiophysicsTechnische Universität DarmstadtGermany
| | | | | | - Gerhard Thiel
- Plant Membrane BiophysicsTechnische Universität DarmstadtGermany
| | - Indra Schroeder
- Plant Membrane BiophysicsTechnische Universität DarmstadtGermany
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13
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Shibnev VA, Deryabin PG, Garaev TM, Finogenova MP, Botikov AG, Mishin DV. Peptide carbocyclic derivatives as inhibitors of the viroporin function of RNA-containing viruses. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2017. [DOI: 10.1134/s1068162017050132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Rauh O, Urban M, Henkes LM, Winterstein T, Greiner T, Van Etten JL, Moroni A, Kast SM, Thiel G, Schroeder I. Identification of Intrahelical Bifurcated H-Bonds as a New Type of Gate in K + Channels. J Am Chem Soc 2017; 139:7494-7503. [PMID: 28499087 PMCID: PMC6638992 DOI: 10.1021/jacs.7b01158] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Gating
of ion channels is based on structural transitions between
open and closed states. To uncover the chemical basis of individual
gates, we performed a comparative experimental and computational analysis
between two K+ channels, KcvS and KcvNTS. These small viral encoded K+ channel proteins, with
a monomer size of only 82 amino acids, resemble the pore module of
all complex K+ channels in terms of structure and function.
Even though both proteins share about 90% amino acid sequence identity,
they exhibit different open probabilities with ca. 90% in KcvNTS and 40% in KcvS. Single channel analysis, mutational
studies and molecular dynamics simulations show that the difference
in open probability is caused by one long closed state in KcvS. This state is structurally created in the tetrameric channel
by a transient, Ser mediated, intrahelical hydrogen bond. The resulting
kink in the inner transmembrane domain swings the aromatic rings from
downstream Phes in the cavity of the channel, which blocks ion flux.
The frequent occurrence of Ser or Thr based helical kinks in membrane
proteins suggests that a similar mechanism could also occur in the
gating of other ion channels.
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Affiliation(s)
- Oliver Rauh
- Plant Membrane Biophysics, Technical University Darmstadt , 64289 Darmstadt, Germany
| | - Martin Urban
- Physikalische Chemie III, Technische Universität Dortmund , 44227 Dortmund, Germany
| | - Leonhard M Henkes
- Physikalische Chemie III, Technische Universität Dortmund , 44227 Dortmund, Germany
| | - Tobias Winterstein
- Plant Membrane Biophysics, Technical University Darmstadt , 64289 Darmstadt, Germany
| | - Timo Greiner
- Plant Membrane Biophysics, Technical University Darmstadt , 64289 Darmstadt, Germany
| | - James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska Lincoln , Lincoln, Nebraska 68583-0900, United States
| | - Anna Moroni
- Department of Biosciences and CNR IBF-Mi, Università degli Studi di Milano , 20122 Milano, Italy
| | - Stefan M Kast
- Physikalische Chemie III, Technische Universität Dortmund , 44227 Dortmund, Germany
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technical University Darmstadt , 64289 Darmstadt, Germany
| | - Indra Schroeder
- Plant Membrane Biophysics, Technical University Darmstadt , 64289 Darmstadt, Germany
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15
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Llabrés S, Juárez-Jiménez J, Masetti M, Leiva R, Vázquez S, Gazzarrini S, Moroni A, Cavalli A, Luque FJ. Mechanism of the Pseudoirreversible Binding of Amantadine to the M2 Proton Channel. J Am Chem Soc 2016; 138:15345-15358. [DOI: 10.1021/jacs.6b07096] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Salomé Llabrés
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
| | - Jordi Juárez-Jiménez
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
| | - Matteo Masetti
- Department
of Pharmacy and Biotecnology (FaBit), Alma Mater Studiorum, University of Bologna, via Belmeloro 6, 40126 Bologna, Italy
| | - Rosana Leiva
- Laboratori
de Química Farmacèutica (Unitat Associada al CSIC),
Facultat de Farmàcia i Ciències de l’Alimentació,
and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan
XXIII 27-31, 08028 Barcelona, Spain
| | - Santiago Vázquez
- Laboratori
de Química Farmacèutica (Unitat Associada al CSIC),
Facultat de Farmàcia i Ciències de l’Alimentació,
and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan
XXIII 27-31, 08028 Barcelona, Spain
| | - Sabrina Gazzarrini
- Department
of Biosciences and National Research Council (CNR) Biophysics Institute
(IBF), University of Milan, Via Celoria 26, 20133 Milan, Italy
| | - Anna Moroni
- Department
of Biosciences and National Research Council (CNR) Biophysics Institute
(IBF), University of Milan, Via Celoria 26, 20133 Milan, Italy
| | - Andrea Cavalli
- Department
of Pharmacy and Biotecnology (FaBit), Alma Mater Studiorum, University of Bologna, via Belmeloro 6, 40126 Bologna, Italy
- CompuNet, Istituto Italiano di Tecnologia (IIT), via Morego 30, 16163 Genova,Italy
| | - F. Javier Luque
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
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16
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Rey-Carrizo M, Gazzarrini S, Llabrés S, Frigolé-Vivas M, Juárez-Jiménez J, Font-Bardia M, Naesens L, Moroni A, Luque FJ, Vázquez S. New polycyclic dual inhibitors of the wild type and the V27A mutant M2 channel of the influenza A virus with unexpected binding mode. Eur J Med Chem 2015; 96:318-29. [DOI: 10.1016/j.ejmech.2015.04.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 04/11/2015] [Accepted: 04/13/2015] [Indexed: 01/08/2023]
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17
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Large dsDNA chloroviruses encode diverse membrane transport proteins. Virology 2015; 479-480:38-45. [PMID: 25766639 DOI: 10.1016/j.virol.2015.02.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/20/2015] [Accepted: 02/07/2015] [Indexed: 10/23/2022]
Abstract
Many large DNA viruses that infect certain isolates of chlorella-like green algae (chloroviruses) are unusual because they often encode a diverse set of membrane transport proteins, including functional K(+) channels and aquaglyceroporins as well as K(+) transporters and calcium transporting ATPases. Some chloroviruses also encode putative ligand-gated-like channel proteins. No one protein is present in all of the chloroviruses that have been sequenced, but the K(+) channel is the most common as only two chloroviruses have been isolated that lack this complete protein. This review describes the properties of these membrane-transporting proteins and suggests possible physiological functions and evolutionary histories for some of them.
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18
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Ritter reaction-mediated syntheses of 2-oxaadamantan-5-amine, a novel amantadine analog. Tetrahedron Lett 2015; 56:1272-1275. [PMID: 32287445 PMCID: PMC7125674 DOI: 10.1016/j.tetlet.2015.01.160] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 01/21/2015] [Accepted: 01/26/2015] [Indexed: 11/22/2022]
Abstract
Two alternative syntheses of 2-oxaadamantan-5-amine, a novel analog of the clinically approved drug amantadine, are reported. The compound has been tested as an anti-influenza A virus agent and as an NMDA receptor antagonist. While the compound was not antivirally active, it displayed moderate activity as an NMDA receptor antagonist.
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19
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Siotto F, Martin C, Rauh O, Van Etten JL, Schroeder I, Moroni A, Thiel G. Viruses infecting marine picoplancton encode functional potassium ion channels. Virology 2014; 466-467:103-11. [PMID: 25441713 DOI: 10.1016/j.virol.2014.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 04/29/2014] [Accepted: 05/03/2014] [Indexed: 01/19/2023]
Abstract
Phycodnaviruses are dsDNA viruses, which infect algae. Their large genomes encode many gene products, like small K(+) channels, with homologs in prokaryotes and eukaryotes. Screening for K(+) channels revealed their abundance in viruses from fresh-water habitats. Recent sequencing of viruses from marine algae or from salt water in Antarctica revealed sequences with the predicted characteristics of K(+) channels but with some unexpected features. Two genes encode either 78 or 79 amino acid proteins, which are the smallest known K(+) channels. Also of interest is an unusual sequence in the canonical α-helixes in K(+) channels. Structural prediction algorithms indicate that the new channels have the conserved α-helix folds but the algorithms failed to identify the expected transmembrane domains flanking the K(+) channel pores. In spite of these unexpected properties electophysiological studies confirmed that the new proteins are functional K(+) channels.
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Affiliation(s)
- Fenja Siotto
- Membrane Biophysics Group, Dept. of Biology, Technical University Darmstadt, Germany
| | - Corinna Martin
- Membrane Biophysics Group, Dept. of Biology, Technical University Darmstadt, Germany
| | - Oliver Rauh
- Membrane Biophysics Group, Dept. of Biology, Technical University Darmstadt, Germany
| | - James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
| | - Indra Schroeder
- Membrane Biophysics Group, Dept. of Biology, Technical University Darmstadt, Germany
| | - Anna Moroni
- Dipartimento di Biologia Università degli Studi di Milano e Istituto di Biofisica, CNR, Milano, Italy
| | - Gerhard Thiel
- Membrane Biophysics Group, Dept. of Biology, Technical University Darmstadt, Germany.
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20
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von Charpuis C, Meckel T, Moroni A, Thiel G. The sorting of a small potassium channel in mammalian cells can be shifted between mitochondria and plasma membrane. Cell Calcium 2014; 58:114-21. [PMID: 25449299 DOI: 10.1016/j.ceca.2014.09.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 09/24/2014] [Accepted: 09/24/2014] [Indexed: 10/24/2022]
Abstract
The two small and similar viral K(+) channels Kcv and Kesv are sorted in mammalian cells and yeast to different destinations. Analysis of the sorting pathways shows that Kcv is trafficking via the secretory pathway to the plasma membrane, while Kesv is inserted via the TIM/TOM complex to the inner membrane of mitochondria. Studies with Kesv mutants show that an N-terminal mitochondrial targeting sequence in this channel is neither necessary nor sufficient for sorting of Kesv the mitochondria. Instead the sorting of Kesv can be redirected from the mitochondria to the plasma membrane by an insertion of ≥2 amino acids in a position sensitive manner into the C-terminal transmembrane domain (TMD2) of this channel. The available data advocate the presence of a C-terminal sorting signal in TMD2 of Kesv channel, which is presumably not determined by the length of this domain.
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Affiliation(s)
- Charlotte von Charpuis
- Plant Membrane Biophysics, TU Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Tobias Meckel
- Plant Membrane Biophysics, TU Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Anna Moroni
- Department of Biology and CNR IBF-Mi, and Istituto Nazionale di Fisica della Materia, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Gerhard Thiel
- Plant Membrane Biophysics, TU Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.
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21
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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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22
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Zhang R, Wang K, Lv W, Yu W, Xie S, Xu K, Schwarz W, Xiong S, Sun B. The ORF4a protein of human coronavirus 229E functions as a viroporin that regulates viral production. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1088-95. [PMID: 23906728 PMCID: PMC7094429 DOI: 10.1016/j.bbamem.2013.07.025] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 07/12/2013] [Accepted: 07/18/2013] [Indexed: 12/29/2022]
Abstract
In addition to a set of canonical genes, coronaviruses encode additional accessory proteins. A locus located between the spike and envelope genes is conserved in all coronaviruses and contains a complete or truncated open reading frame (ORF). Previously, we demonstrated that this locus, which contains the gene for accessory protein 3a from severe acute respiratory syndrome coronavirus (SARS-CoV), encodes a protein that forms ion channels and regulates virus release. In the current study, we explored whether the ORF4a protein of HCoV-229E has similar functions. Our findings revealed that the ORF4a proteins were expressed in infected cells and localized at the endoplasmic reticulum/Golgi intermediate compartment (ERGIC). The ORF4a proteins formed homo-oligomers through disulfide bridges and possessed ion channel activity in both Xenopus oocytes and yeast. Based on the measurement of conductance to different monovalent cations, the ORF4a was suggested to form a non-selective channel for monovalent cations, although Li(+) partially reduced the inward current. Furthermore, viral production decreased when the ORF4a protein expression was suppressed by siRNA in infected cells. Collectively, this evidence indicates that the HCoV-229E ORF4a protein is functionally analogous to the SARS-CoV 3a protein, which also acts as a viroporin that regulates virus production. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.
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Affiliation(s)
- Ronghua Zhang
- Jiangsu Key Laboratory of Infection and Immunity, Institutes of Biology and Medical Sciences, Soochow University, Suzhou 215123, China; Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Kai Wang
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Wei Lv
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Wenjing Yu
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Shiqi Xie
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Ke Xu
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China
| | - Wolfgang Schwarz
- Goethe-University Frankfurt, Institute for Biophysics, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany; Shanghai Research Center for Acupuncture and Meridian, 199 Guoshoujing Road, Shanghai 201023, China
| | - Sidong Xiong
- Jiangsu Key Laboratory of Infection and Immunity, Institutes of Biology and Medical Sciences, Soochow University, Suzhou 215123, China.
| | - Bing Sun
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200025, China; State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
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23
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Thiel G, Moroni A, Blanc G, Van Etten JL. Potassium ion channels: could they have evolved from viruses? PLANT PHYSIOLOGY 2013; 162:1215-24. [PMID: 23719891 PMCID: PMC3707557 DOI: 10.1104/pp.113.219360] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 05/23/2013] [Indexed: 06/01/2023]
Abstract
Phylogenetic analyses of small viral K+ channels suggests that they did not originate from their hosts, but instead could be the source of the postulated pore precursor in the evolution of K+ channels.
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Affiliation(s)
- Gerhard Thiel
- Department of Biology, Technische Universität-Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.
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24
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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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25
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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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26
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Using yeast to study potassium channel function and interactions with small molecules. Methods Mol Biol 2013; 995:31-42. [PMID: 23494370 DOI: 10.1007/978-1-62703-345-9_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Analysis of ion channel mutants is a widely used approach for dissecting ion channel function and for characterizing the mechanisms of action of channel-directed modulators. Expression of functional potassium channels in potassium-uptake-deficient yeast together with genetic selection approaches offers an unbiased, high-throughput, activity-based readout that can rapidly identify large numbers of active ion channel mutants. Because of the assumption-free nature of the method, detailed biophysical analysis of the functional mutants from such selections can provide new and unexpected insights into both ion channel gating and ion channel modulator mechanisms. Here, we present detailed protocols for generation and identification of functional mutations in potassium channels using yeast selections in the potassium-uptake-deficient strain SGY1528. This approach is applicable for the analysis of structure-function relationships of potassium channels from a wide range of sources including viruses, bacteria, plants, and mammals and can be used as a facile way to probe the interactions between ion channels and small-molecule modulators.
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27
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Herrero L, Monroy N, González ME. HIV-1 Vpu Protein Mediates the Transport of Potassium in Saccharomyces cerevisiae. Biochemistry 2012; 52:171-7. [DOI: 10.1021/bi3011175] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Laura Herrero
- Unidad de Expresión Viral, Centro
Nacional de
Microbiología, Instituto de Salud Carlos III, Carretera de
Majadahonda-Pozuelo Km 2, 28220 Majadahonda, Madrid, Spain
| | - Noemí Monroy
- Unidad de Expresión Viral, Centro
Nacional de
Microbiología, Instituto de Salud Carlos III, Carretera de
Majadahonda-Pozuelo Km 2, 28220 Majadahonda, Madrid, Spain
| | - María Eugenia González
- Unidad de Expresión Viral, Centro
Nacional de
Microbiología, Instituto de Salud Carlos III, Carretera de
Majadahonda-Pozuelo Km 2, 28220 Majadahonda, Madrid, Spain
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28
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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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29
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Van Etten JL, Dunigan DD. Chloroviruses: not your everyday plant virus. TRENDS IN PLANT SCIENCE 2012; 17:1-8. [PMID: 22100667 PMCID: PMC3259250 DOI: 10.1016/j.tplants.2011.10.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/20/2011] [Accepted: 10/25/2011] [Indexed: 05/29/2023]
Abstract
Viruses infecting higher plants are among the smallest viruses known and typically have four to ten protein-encoding genes. By contrast, many viruses that infect algae (classified in the virus family Phycodnaviridae) are among the largest viruses found to date and have up to 600 protein-encoding genes. This brief review focuses on one group of plaque-forming phycodnaviruses that infect unicellular chlorella-like green algae. The prototype chlorovirus PBCV-1 has more than 400 protein-encoding genes and 11 tRNA genes. About 40% of the PBCV-1 encoded proteins resemble proteins of known function including many that are completely unexpected for a virus. In many respects, chlorovirus infection resembles bacterial infection by tailed bacteriophages.
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Affiliation(s)
- James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA.
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30
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Greiner T, Ramos J, Alvarez MC, Gurnon JR, Kang M, Van Etten JL, Moroni A, Thiel G. Functional HAK/KUP/KT-like potassium transporter encoded by chlorella viruses. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:977-986. [PMID: 21848655 DOI: 10.1111/j.1365-313x.2011.04748.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Chlorella viruses are a source of interesting membrane transport proteins. Here we examine a putative K(+) transporter encoded by virus FR483 and related chlorella viruses. The protein shares sequence and structural features with HAK/KUP/KT-like K(+) transporters from plants, bacteria and fungi. Yeast complementation assays and Rb(+) uptake experiments show that the viral protein, termed HAKCV (high-affinity K(+) transporter of chlorella virus), is functional, with transport characteristics that are similar to those of known K(+) transporters. Expression studies revealed that the protein is expressed as an early gene during viral replication, and proteomics data indicate that it is not packaged in the virion. The function of HAKCV is unclear, but the data refute the hypothesis that the transporter acts as a substitute for viral-encoded K(+) channels during virus infection.
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Affiliation(s)
- Timo Greiner
- Institute of Botany at the Technische Universität Darmstadt, Schnittspahnstrasse 3-5, 64287 Darmstadt, Germany
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Song WY, Hörtensteiner S, Tomioka R, Lee Y, Martinoia E. Common functions or only phylogenetically related? The large family of PLAC8 motif-containing/PCR genes. Mol Cells 2011; 31:1-7. [PMID: 21347707 PMCID: PMC3906873 DOI: 10.1007/s10059-011-0024-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 12/09/2010] [Indexed: 11/27/2022] Open
Abstract
PLAC8 motif-containing proteins form a large family and members can be found in fungi, algae, higher plants and animals. They include the PCR proteins of plants. The name giving PLAC8 domain was originally found in a protein residing in the spongiotrophoblast layer of the placenta of mammals. A further motif found in a large number of these proteins including several PCR proteins is the CCXXXXCPC or CLXXXXCPC motif. Despite their wide distribution our knowledge about the function of these proteins is very limited. For most of them two membrane-spanning α-helices are predicted, indicating that they are membrane associated or membrane intrinsic proteins. In plants PLAC8 motif-containing proteins have been described to be implicated in two very different functions. On one hand, it has been shown that they are involved in the determination of fruit size and cell number. On the other hand, two members of this family, AtPCR1 and AtPCR2 play an important role in transport of heavy metals such as cadmium or zinc. Transport experiments and approaches to model the 3_D structure of these proteins indicate that they could act as transporters for these divalent cations by forming homomultimers. In this minireview we discuss the present knowledge about this protein family and try to give an outlook on how to integrate the different proposed functions into a common picture about the role of PLAC8 motif-containing proteins.
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Affiliation(s)
- Won-Yong Song
- Institute of Plant Biology, University Zurich, Zurich, Switzerland
- POSTECH-UZH Cooperative Laboratory, Department of Integrative Bioscience and Biotechnology, World Class University Program, Pohang University of Science and Technology, Pohang 790-784, Korea
| | | | - Rie Tomioka
- Institute of Plant Biology, University Zurich, Zurich, Switzerland
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Youngsook Lee
- POSTECH-UZH Cooperative Laboratory, Department of Integrative Bioscience and Biotechnology, World Class University Program, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Enrico Martinoia
- Institute of Plant Biology, University Zurich, Zurich, Switzerland
- POSTECH-UZH Cooperative Laboratory, Department of Integrative Bioscience and Biotechnology, World Class University Program, Pohang University of Science and Technology, Pohang 790-784, Korea
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Song WY, Choi KS, Kim DY, Geisler M, Park J, Vincenzetti V, Schellenberg M, Kim SH, Lim YP, Noh EW, Lee Y, Martinoia E. Arabidopsis PCR2 is a zinc exporter involved in both zinc extrusion and long-distance zinc transport. THE PLANT CELL 2010; 22:2237-52. [PMID: 20647347 PMCID: PMC2929092 DOI: 10.1105/tpc.109.070185] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 06/13/2010] [Accepted: 07/01/2010] [Indexed: 05/19/2023]
Abstract
Plants strictly regulate the uptake and distribution of Zn, which is essential for plant growth and development. Here, we show that Arabidopsis thaliana PCR2 is essential for Zn redistribution and Zn detoxification. The pcr2 loss-of-function mutant was compromised in growth, both in Zn-excessive and -deficient conditions. The roots of pcr2 accumulated more Zn than did control plants, whereas the roots of plants overexpressing PCR2 contained less Zn, indicating that PCR2 removes Zn from the roots. Consistent with a role for PCR2 as a Zn-efflux transporter, PCR2 reduced the intracellular concentration of Zn when expressed in yeast cells. PCR2 is located mainly in epidermal cells and in the xylem of young roots, while it is expressed in epidermal cells in fully developed roots. Zn accumulated in the epidermis of the roots of pcr2 grown under Zn-limiting conditions, whereas it was found in the stele of wild-type roots. The transport pathway mediated by PCR2 does not seem to overlap with that mediated by the described Zn translocators (HMA2 and HMA4) since the growth of pcr2 hma4 double and pcr2 hma2 hma4 triple loss-of-function mutants was more severely inhibited than the individual single knockout mutants, both under conditions of excess or deficient Zn. We propose that PCR2 functions as a Zn transporter essential for maintaining an optimal Zn level in Arabidopsis.
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Affiliation(s)
- Won-Yong Song
- Institut für Pflanzenbiologie, Universität Zürich, 8008 Zurich, Switzerland.
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Clarke OB, Caputo AT, Hill AP, Vandenberg JI, Smith BJ, Gulbis JM. Domain Reorientation and Rotation of an Intracellular Assembly Regulate Conduction in Kir Potassium Channels. Cell 2010; 141:1018-29. [DOI: 10.1016/j.cell.2010.05.003] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Wang K, Xie S, Sun B. Viral proteins function as ion channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:510-5. [PMID: 20478263 PMCID: PMC7094589 DOI: 10.1016/j.bbamem.2010.05.006] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 04/30/2010] [Accepted: 05/06/2010] [Indexed: 11/26/2022]
Abstract
Viral ion channels are short membrane proteins with 50–120 amino acids and play an important role either in regulating virus replication, such as virus entry, assembly and release or modulating the electrochemical balance in the subcellular compartments of host cells. This review summarizes the recent advances in viral encoded ion channel proteins (or viroporins), including PBCV-1 KcV, influenza M2, HIV-1 Vpu, HCV p7, picornavirus 2B, and coronavirus E and 3a. We focus on their function and mechanisms, and also discuss viral ion channel protein serving as a potential drug target.
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Affiliation(s)
- Kai Wang
- Laboratory of Molecular Virology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 225 South Chongqing Road, Shanghai 200025, China
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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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36
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Tan Q, Shim JW, Gu LQ. Separation of heteromeric potassium channel Kcv towards probing subunit composition-regulated ion permeation and gating. FEBS Lett 2010; 584:1602-8. [PMID: 20303961 DOI: 10.1016/j.febslet.2010.03.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 03/12/2010] [Accepted: 03/15/2010] [Indexed: 11/19/2022]
Abstract
The chlorella virus-encoded Kcv can form a homo-tetrameric potassium channel in lipid membranes. This miniature peptide can be synthesized in vitro, and the tetramer purified from the SDS-polyacrylamide gel retains the K(+) channel functionality. Combining this capability with the mass-tagging method, we propose a simple, straightforward approach that can generically manipulate individual subunits in the tetramer, thereby enabling the detection of contribution from individual subunits to the channel functions. Using this approach, we showed that the structural change in the selectivity filter from only one subunit is sufficient to cause permanent channel inactivation ("all-or-none" mechanism), whereas the mutation near the extracellular entrance additively modifies the ion permeation with the number of mutant subunits in the tetramer ("additive" mechanism).
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Affiliation(s)
- Qiulin Tan
- Department of Biological Engineering, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
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Chatelain FC, Gazzarrini S, Fujiwara Y, Arrigoni C, Domigan C, Ferrara G, Pantoja C, Thiel G, Moroni A, Minor DL. Selection of inhibitor-resistant viral potassium channels identifies a selectivity filter site that affects barium and amantadine block. PLoS One 2009; 4:e7496. [PMID: 19834614 PMCID: PMC2759520 DOI: 10.1371/journal.pone.0007496] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 09/23/2009] [Indexed: 12/02/2022] Open
Abstract
Background Understanding the interactions between ion channels and blockers remains an important goal that has implications for delineating the basic mechanisms of ion channel function and for the discovery and development of ion channel directed drugs. Methodology/Principal Findings We used genetic selection methods to probe the interaction of two ion channel blockers, barium and amantadine, with the miniature viral potassium channel Kcv. Selection for Kcv mutants that were resistant to either blocker identified a mutant bearing multiple changes that was resistant to both. Implementation of a PCR shuffling and backcrossing procedure uncovered that the blocker resistance could be attributed to a single change, T63S, at a position that is likely to form the binding site for the inner ion in the selectivity filter (site 4). A combination of electrophysiological and biochemical assays revealed a distinct difference in the ability of the mutant channel to interact with the blockers. Studies of the analogous mutation in the mammalian inward rectifier Kir2.1 show that the T→S mutation affects barium block as well as the stability of the conductive state. Comparison of the effects of similar barium resistant mutations in Kcv and Kir2.1 shows that neighboring amino acids in the Kcv selectivity filter affect blocker binding. Conclusions/Significance The data support the idea that permeant ions have an integral role in stabilizing potassium channel structure, suggest that both barium and amantadine act at a similar site, and demonstrate how genetic selections can be used to map blocker binding sites and reveal mechanistic features.
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Affiliation(s)
- Franck C. Chatelain
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Sabrina Gazzarrini
- Dipartimento di Biologia e Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, Milan, Italy
| | - Yuichiro Fujiwara
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Cristina Arrigoni
- Dipartimento di Biologia e Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, Milan, Italy
| | - Courtney Domigan
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Giuseppina Ferrara
- Dipartimento di Biologia e Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, Milan, Italy
| | - Carlos Pantoja
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
| | - Gerhard Thiel
- Technische Universität Darmstadt, Institute für Botanik, Darmstadt, Germany
| | - Anna Moroni
- Dipartimento di Biologia e Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, Milan, Italy
| | - Daniel L. Minor
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
- Department of California Institute for Quantitative Biomedical Research, University of California San Francisco, San Francisco, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- * E-mail:
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