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Crystal structure and molecular imaging of the Nav channel β3 subunit indicates a trimeric assembly

DOI: 10.1074/jbc.M113.527994 DOI Help
PMID: 24567321 PMID Help

Authors: Sivakumar Namadurai (Department of Biochemistry, University of Cambridge) , D. Balasuriya (Department of Pharmacology, University of Cambridge) , R. Rajappa (Institute of Medical Physics and Biophysics, University of Münster) , M. Wiemhofer (Institute of Medical Physics and Biophysics, University of Münster) , K. Stott (Department of Biochemistry, University of Cambridge) , J. Klingauf (Institute of Medical Physics and Biophysics, University of Münster) , J. M. Edwardson (Department of Pharmacology, University of Cambridge) , Dima Chirgadze (Department of Biochemistry, University of Cambridge) , A. P. Jackson (Department of Biochemistry, University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry , VOL 289 (15) , PAGES 10797 - 10811

State: Published (Approved)
Published: April 2014

Open Access Open Access

Abstract: The vertebrate sodium (Nav) channel is composed of an ion-conducting alpha subunit and associated beta subunits. Here, we report the crystal structure of the human beta 3 subunit immunoglobulin (Ig) domain, a functionally important component of Nav channels in neurons and cardiomyocytes. Surprisingly, we found that the beta 3 subunit Ig domain assembles as a trimer in the crystal asymmetric unit. Analytical ultracentrifugation confirmed the presence of Ig domain monomers, dimers, and trimers in free solution, and atomic force microscopy imaging also detected full-length beta 3 subunit monomers, dimers, and trimers. Mutation of a cysteine residue critical for maintaining the trimer interface destabilized both dimers and trimers. Using fluorescence photoactivated localization microscopy, we detected full-length beta 3 subunit trimers on the plasma membrane of transfected HEK293 cells. We further show that beta3 subunits can bind to more than one site on the Nav 1.5 alpha subunit and induce the formation of alpha subunit oligomers, including trimers. Our results suggest a new and unexpected role for the beta3 subunits in Nav channel cross-linking and provide new structural insights into some pathological Nav channel mutations.

Journal Keywords: Binding; Cloning; Molecular; Crystallization; Crystallography; X-Ray; Dimerization; HEK293; Humans; Immunoglobulins; Microscopy; Atomic; NAV1.5; Protein; Ultracentrifugation; Voltage-Gated Sodium Channel beta-3 Subunit

Subject Areas: Biology and Bio-materials


Instruments: I04-Macromolecular Crystallography

Documents:
J. Biol. Chem.-2014-Namadurai-10797-811.pdf

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