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1 Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA
2 Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
3 The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
(RECEIVED March 12, 2007; FINAL REVISION June 1, 2007; ACCEPTED June 5, 2007)
The potassium channel accessory subunit KChIP2 associates with Kv4.2 channels in the cardiac myocyte and is involved in the regulation of the transient outward current (Ito) during the early phase of repolarization of the action potential. As a first step to biophysically probe the mechanism of KChIP2, we have chemically synthesized its minimal isoform, KChIP2d, using Boc chemistry solid phase peptide synthesis in conjunction with native chemical ligation. The synthetic KChIP2d protein is primarily alpha-helical as predicted and becomes more structured upon binding calcium as assessed by 1H-NMR and CD spectroscopy. Synthetic KChIP2d is in a monomer-dimer equilibrium in solution, and there is evidence for two monomer binding sites on an N-terminal peptide of Kv4.2. Planned future studies include the incorporation of fluorescent and spin labeled probes in KChIP2d to yield structural information in parallel with electrophysiologic studies to elucidate KChIP2d's mechanism of action.
Keywords: potassium channel; accessory subunit; total chemical synthesis; kinetically controlled ligation; Boc chemistry solid phase peptide synthesis
Reprint requests to: Sudarshan Rajagopal, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA; e-mail: rajag007{at}mc.duke.edu; fax: (919) 681-6448.
Article published online ahead of print. Article and publication date are at http://www.proteinscience.org/cgi/doi/10.1110/ps.072876107.
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