hERG encodes the pore-forming subunit of the rapidly-activating delayed-rectifier potassium channel, which is important for cardiac repolarization.

hERG potassium channels are essential for normal electrical activity in the heart. Dysfunction of hERG causes long QT syndrome and sudden death. Drug binding (predominantly to serum protein) may result in decreased channel function and drug-induced (acquired) long QT syndrome. Antibacterial drugs that can cause QT prolongation include quinolones and macrolides.

See also: QT study