| The activated state of a sodium channel voltage sensor in a membrane environment. | |
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MedLine Citation:
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PMID: 20207950 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Direct structural insights on the fundamental mechanisms of permeation, selectivity, and gating remain unavailable for the Na(+) and Ca(2+) channel families. Here, we report the spectroscopic structural characterization of the isolated Voltage-Sensor Domain (VSD) of the prokaryotic Na(+) channel NaChBac in a lipid bilayer. Site-directed spin-labeling and EPR spectroscopy were carried out for 118 mutants covering all of the VSD. EPR environmental data were used to unambiguously assign the secondary structure elements, define membrane insertion limits, and evaluate the activated conformation of the isolated-VSD in the membrane using restrain-driven molecular dynamics simulations. The overall three-dimensional fold of the NaChBac-VSD closely mirrors those seen in KvAP, Kv1.2, Kv1.2-2.1 chimera, and MlotiK1. However, in comparison to the membrane-embedded KvAP-VSD, the structural dynamics of the NaChBac-VSD reveals a much tighter helix packing, with subtle differences in the local environment of the gating charges and their interaction with the rest of the protein. Using cell complementation assays we show that the NaChBac-VSD can provide a conduit to the transport of ions in the resting or "down" conformation, a feature consistent with our EPR water accessibility measurements in the activated or "up" conformation. These results suggest that the overall architecture of VSD's is remarkably conserved among K(+) and Na(+) channels and that pathways for gating-pore currents may be intrinsic to most voltage-sensors. Cell complementation assays also provide information about the putative location of the gating charges in the "down/resting" state and hence a glimpse of the extent of conformational changes during activation. |
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Authors:
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Sudha Chakrapani; Pornthep Sompornpisut; Pathumwadee Intharathep; Benoît Roux; Eduardo Perozo |
Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't Date: 2010-03-05 |
Journal Detail:
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Title: Proceedings of the National Academy of Sciences of the United States of America Volume: 107 ISSN: 1091-6490 ISO Abbreviation: Proc. Natl. Acad. Sci. U.S.A. Publication Date: 2010 Mar |
Date Detail:
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Created Date: 2010-03-24 Completed Date: 2010-04-16 Revised Date: 2010-09-24 |
Medline Journal Info:
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Nlm Unique ID: 7505876 Medline TA: Proc Natl Acad Sci U S A Country: United States |
Other Details:
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Languages: eng Pagination: 5435-40 Citation Subset: IM |
Affiliation:
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Department of Biochemistry and Molecular Biology, University of Chicago, Center for Integrative Science, 929 East 57th Street, Chicago, IL 60637, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Bacterial Proteins
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chemistry*,
metabolism* Biophysical Phenomena Electron Spin Resonance Spectroscopy Ion Channel Gating Lipid Bilayers Models, Molecular Molecular Dynamics Simulation Protein Conformation Protein Structure, Tertiary Recombinant Proteins / chemistry, metabolism Sodium Channels / chemistry*, metabolism* Thermodynamics Water |
| Grant Support | |
ID/Acronym/Agency:
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GM057846/GM/NIGMS NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Bacterial Proteins; 0/Lipid Bilayers; 0/NaChBac protein, bacteria; 0/Recombinant Proteins; 0/Sodium Channels; 7732-18-5/Water |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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