抄録
KCNQ1 is a voltage-dependent K+ channel whose gating property is dramatically changed by association of auxiliary KCNE proteins. KCNE1, which is mainly expressed in heart, drastically decelerates the activation kinetics of KCNQ1. However, the question if the voltage-sensing S4 domain moves differently with KCNE1 has not been revealed yet. To address this point by MTSET accessibility analysis, we systematically introduced cysteine mutations one at a time to the first half of S4 domain of human KCNQ1 gene. These mutants were expressed in Xenopus oocytes and analyzed under two-electrode voltage clamp. Before the MTSET experiments, we first characterized the properties of mutants. Unexpectedly, we observed that some of these mutants (I227C, R228C, G229C, I230C, F232C, L233C) showed extremely slow deactivation, and as a result, they eventually became constitutively-active after several times of depolarization. However, this phenotype was waned or completely gone with co-expression of KCNE1 except in G229C, which became constitutively active more easily than without KCNE1. For the analysis of MTSET accessibility, KCNQ1 mutants were incubated in 98 mM K+ extracellular solution with 1 mM MTSET for 30 min. When KCNE1 was co-expressed, G229C and I230C became constitutively active by MTSET while they were only partially activated by MTSET in the absence of KCNE1. Taken together, these results suggest that association of KCNE1 change molecular environments of S4 domain of KCNQ1. [J Physiol Sci. 2007;57 Suppl:S230]
