HERG K+ channels: friend and foe.

The K+ channel encoded by the human ether-à-go-go related gene (HERG) is one of many ion channels that are crucial for normal action potential repolarization in cardiac myocytes. HERG encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, I(K(Vr)). HERG K+ channels are of considerable pharmaceutical interest as possible therapeutic targets for anti-arrhythmic agents and as the molecular target responsible for the cardiac toxicity of a wide range of pharmaceutical agents. Recent studies of the molecular basis of the promiscuity of HERG K+ channel drug binding has not only started to shed light on this tricky pharmaceutical problem but has also provided further insights into the structure and function of HERG K+ channels.