Potassium voltage-gated channel subfamily H member 2 (HERG) is the pore-forming (alpha) subunit of voltage-gated inwardly rectifying potassium channel. The HERG channel properties are modulated by cAMP and subunit assembly. HERG mediates the rapidly activating component of the delayed rectifying potassium current in heart (IKr). Isoform 3 has no channel activity by itself, but modulates channel characteristics when associated with isoform 1. Defects in HERG are the cause of long QT syndrome type 2 (LQT2). Long QT syndromes are heart disorders characterized by a prolonged QT interval on the ECG and polymorphic ventricular arrhythmias. They cause syncope and sudden death in response to e, Xenopus/Amphibian,ercise or emotional stress.