Increase of the single-channel conductance of KvLQT1 potassium channels induced by the association with minK.
Gating of the delayed rectifier K+ channel KvLQT1 is drastically slowed by the association with the small membrane protein minK and it is thought that the KvLQT1/minK complex underlies the slow delayed rectifier K+ current of cardiac cells. There is controversy about the effects of the association between KvLQT1 and minK on the single-channel conductance. Here, nonstationary fluctuation analysis was applied to inward K+ tail currents recorded with a high-time resolution (5 kHz bandwidth) from macropatches of homomeric KvLQT1 and heteromeric KvLQT1/minK channels expressed in Xenopus oocytes to estimate their single-channel conductance. It was found that heteromers have a threefold larger conductance (5.8 pS) compared to homomeric channels (1.8 pS) in symmetrical high-K+ solutions. The larger conductance of heteromers explains in part their larger macroscopic conductance in heterologous expression systems. The molecular mechanism underlying the conductance increase remains to be identified.
Pusch
M
M
Istituto di Cibernetica e Biofisica, CNR, Via de Marini 6, I-16149 Genova, Italy. pusch@barolo.icb.ge.cnr.it
D000818:Animals; D004553:Electric Conductivity; D005260:Female; D006801:Humans; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014981:Xenopus
D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; C059983:potassium channel protein I(sk)