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J. Biol. Chem., Vol. 283, Issue 22, 15072-15077, May 30, 2008

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I_SA Channel Complexes Include Four Subunits Each of DPP6 and Kv4.2^*

From the Department of Pediatrics and Institute for Molecular Pediatric Sciences, Pritzker School of Medicine, Biological Sciences Division, University of Chicago, Chicago, Illinois 60637

Kv4 potassium channels produce rapidly inactivating currents that regulate excitability of muscles and nerves. To reconstitute the neuronal A-type current I_SA, Kv4 subunits assemble with DPP6, a single transmembrane domain accessory subunit. DPP6 alters function—accelerating activation, inactivation, and recovery from inactivation—and increases surface expression. We sought here to determine the stoichiometry of Kv4 and DPP6 in complexes using functional and biochemical methods. First, wild type channels formed from subunit monomers were compared with channels carrying subunits linked in tandem to enforce 4:4 and 4:2 assemblies (Kv4.2-DPP6 and Kv4.2-Kv4.2-DPP6). Next, channels were overexpressed and purified so that the molar ratio of subunits in complexes could be assessed by direct amino acid analysis. Both biophysical and biochemical methods indicate that I_SA channels carry four subunits each of Kv4.2 and DPP6.

Received for publication, August 20, 2007

^* This work was supported, in whole or in part, by National Institutes of Health Grant GM051851. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Supported by Korea Research Foundation Grant KRF-2003-037-C00100.

² To whom correspondence should be addressed: Dept. of Pediatrics and Institute for Molecular Pediatric Sciences, Pritzker School of Medicine, Biological Sciences Division, University of Chicago, 5721 S. Maryland Ave., Chicago, IL 60637. E-mail: sangoldstein{at}uchicago.edu.

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