Calcium-dependent gating of MthK, a prokaryotic potassium channel. Academic Article uri icon

Overview

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.

publication date

  • June 1, 2006

Research

keywords

  • Archaeal Proteins
  • Calcium
  • Ion Channel Gating
  • Methanobacterium
  • Potassium Channels

Identity

PubMed Central ID

  • PMC2151542

Scopus Document Identifier

  • 33744478874

Digital Object Identifier (DOI)

  • 10.1085/jgp.200609534

PubMed ID

  • 16735753

Additional Document Info

volume

  • 127

issue

  • 6