Structural Superimposition

Abstact

Escherichia coli has a single K(+) channel gene, kch, that produces a K(+) channel with six transmembrane segments and a cytosolic Regulate Conductance of K(+) channels (RCK) domain. RCK domains are present in both eukaryotic and prokaryotic organisms and known to regulate ion channel activity upon binding of an ion or a nucleotide, however, how Kch is regulated remains unknown. Here, we show that Zn(2+) or Cu(2+) activates Kch via the RCK domain. Structural studies reveal that eight RCK domains assemble into a gating ring that can assume three conformations, closed, intermediate, and open, and that Zn(2+) promotes the open conformation by stabilizing the assembly interface. These results expand our knowledge on Kch and on RCK-mediated regulation of ion channels.