Two pore residues mediate acidosis-induced enhancement of C-type inactivation of the Kv1.4 K(+) channel.
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 Delta2-146) was expressed in Xenopus oocytes, and currents were recorded using two-microelectrode voltage clamp. Acidosis increased fKv1.4 Delta2-146 C-type inactivation. Replacement of a pore histidine with cysteine (H508C) abolished the increase. Application of positively charged thiol-specific methanethiosulfonate to fKv1.4 Delta2-146 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.
Claydon
T W
TW
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
Boyett
M R
MR
Sivaprasadarao
A
A
Orchard
C H
CH
D000138:Acidosis / Q000139:chemically induced / Q000378:metabolism*; D000143:Acids / Q000494:pharmacology; D000468:Alkalies / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D005289:Ferrets; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D051665:Kv1.4 Potassium Channel; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D008845:Microinjections; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D015202:Protein Engineering; D018075:RNA, Complementary / Q000378:metabolism; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D000143:Acids; D000468:Alkalies; D051665:Kv1.4 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D018075:RNA, Complementary