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Am J Physiol Cell Physiol (June 13, 2002). doi:10.1152/ajpcell.00542.2001
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Articles in PresS, published online ahead of print June 13, 2002
Am J Physiol Cell Physiol, 10.1152/ajpcell.00542.2001
Submitted on November 16, 2001
Accepted on June 5, 2002

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

Thomas W. Claydon1, Mark R. Boyett1*, Asipu Sivaprasadarao1, and Clive H. Orchard1

1 School of Biomedical Sciences, University of Leeds, Leeds, West Yorkshire, United Kingdom

* To whom correspondence should be addressed. E-mail: m.r.boyett{at}leeds.ac.uk.

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 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 methanethiosulphonate 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 acidosis-induced increase of C-type inactivation involves the charge on H508 and K532.




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