CALCIUM ACTIVATION OF K+ CHANNELS: RCK DOMAINS

Abstract

Some K+ channels can be activated by a rise in cytosolic Ca2+ and, in two cases (the K+ channels from the archeon Methanobacterium thermoautotrophicum (MthK) and the large conductance voltage- and Ca2+-activated K+ (BK) channel), the Ca2+-binding sites are contained within the regulatory domains for K+conductance (RCK). The MthK channel is a tetramer formed by subunits containing two transmembrane domains and a C-terminal domain containing a single RCK domain (Jiang et al. 2002). The functional MthK channel, however, contains eight RCK domains, and the green domains in Fig. 1a come from the cytoplasmic milieu.