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Am J Physiol Cell Physiol 283: C1114-C1121, 2002. First published June 13, 2002; doi:10.1152/ajpcell.00542.2001
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Vol. 283, Issue 4, C1114-C1121, October 2002

Two pore residues mediate acidosis-induced enhancement of C-type inactivation of the Kv1.4 K+ channel

T. W. Claydon, M. R. Boyett, A. Sivaprasadarao, and C. H. Orchard

School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom

Acidosis inhibits current through the Kv1.4 K+ channel, perhaps as a result of enhancement of C-type inactivation. The mechanism of action of acidosis on C-type inactivation has been studied. A mutant Kv1.4 channel that lacks N-type inactivation (fKv1.4 Delta 2-146) was expressed in Xenopus oocytes, and currents were recorded using two-microelectrode voltage clamp. Acidosis increased fKv1.4 Delta 2-146 C-type inactivation. Replacement of a pore histidine with cysteine (H508C) abolished the increase. Application of positively charged thiol-specific methanethiosulfonate to fKv1.4 Delta 2-146 H508C increased C-type inactivation, mimicking the effect of acidosis. Replacement of a pore lysine with cysteine (K532C) abolished the acidosis-induced increase of C-type inactivation. A model of the Kv1.4 pore, based on the crystal structure of KcsA, shows that H508 and K532 lie close together. It is suggested that the acidosis-induced increase of C-type inactivation involves the charge on H508 and K532.

acidosis; C-type inactivation; Kv1.4


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