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Protein Science (2008), 17:506-517. Published by Cold Spring Harbor Laboratory Press. Copyright © 2008 The Protein Society
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The structure of the lipid-embedded potassium channel voltage sensor determined by double-electron–electron resonance spectroscopy

Magdalini Vamvouka1, John Cieslak1, Ned Van Eps2, Wayne Hubbell2, and Adrian Gross1

1 Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA
2 Jules Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, California 90095, USA

(RECEIVED October 23, 2007; FINAL REVISION December 5, 2007; ACCEPTED December 7, 2007)

A four-pulse electron paramagnetic resonance experiment was used to measure long-range inter-subunit distances in reconstituted KvAP, a voltage-dependent potassium (Kv) channel. The measurements have allowed us to reach the following five conclusions about the native structure of the voltage sensor of KvAP. First, the S1 helix of the voltage sensor engages in a helix packing interaction with the pore domain. Second, the crystallographically observed antiparallel helix-turn-helix motif of the voltage-sensing paddle is retained in the membrane-embedded voltage sensor. Third, the paddle is oriented in such a way as to expose one face to the pore domain and the opposite face to the membrane. Fourth, the paddle and the pore domain appear to be separated by a gap that is sufficiently wide for lipids to penetrate between the two domains. Fifth, the critical voltage-sensing arginine residues on the paddle appear to be lipid exposed. These results demonstrate the importance of the membrane for the native structure of Kv channels, suggest that lipids are an integral part of their native structure, and place the voltage-sensing machinery into a complex lipid environment near the pore domain.

Keywords: electron spin resonance spectroscopy; potassium channels; voltage-gated; protein conformation


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