Title | Calcium-dependent gating of MthK, a prokaryotic potassium channel. |
Publication Type | Journal Article |
Year of Publication | 2006 |
Authors | Zadek B, Nimigean CM |
Journal | J Gen Physiol |
Volume | 127 |
Issue | 6 |
Pagination | 673-85 |
Date Published | 2006 Jun |
ISSN | 0022-1295 |
Keywords | Archaeal Proteins, Calcium, Ion Channel Gating, Methanobacterium, Potassium Channels |
Abstract | MthK is a calcium-gated, inwardly rectifying, prokaryotic potassium channel. Although little functional information is available for MthK, its high-resolution structure is used as a model for eukaryotic Ca(2+)-dependent potassium channels. Here we characterize in detail the main gating characteristics of MthK at the single-channel level with special focus on the mechanism of Ca(2+) activation. MthK has two distinct gating modes: slow gating affected mainly by Ca(2+) and fast gating affected by voltage. Millimolar Ca(2+) increases MthK open probability over 100-fold by mainly increasing the frequency of channel opening while leaving the opening durations unchanged. The Ca(2+) dose-response curve displays an unusually high Hill coefficient (n = approximately 8), suggesting strong coupling between Ca(2+) binding and channel opening. Depolarization affects both the fast gate by dramatically reducing the fast flickers, and to a lesser extent, the slow gate, by increasing MthK open probability. We were able to capture the mechanistic features of MthK with a modified MWC model. |
DOI | 10.1085/jgp.200609534 |
Alternate Journal | J. Gen. Physiol. |
PubMed ID | 16735753 |
PubMed Central ID | PMC2151542 |