KcsA - Prokaryotic pH-gated Potassium Channel
Prokaryotic Tetrameric Potassium Channels
The channel protein contains two transmembrane helices (M1 and M2). The channel itself is a tetramer composed of four identical subunits so that the M2 helix faces the central pore, while the other M1 helix faces the lipid membrane.
History and function:
KcsA was the first potassium ion channel to be characterized using x-ray crystallography by Roderick MacKinnon and his colleagues in 1998. As one of the most studied ion channels to this day, KcsA is a template for research on K+ channel function. The KcsA channel is considered a model channel because its structure provides a framework for understanding K+ channel conduction, which has three parts: Potassium selectivity, channel gating by pH sensitivity, and voltage-gated channel inactivation.