The function of ENSG00000055118 (KCNH2, potassium voltage-gated channel subfamily H member 2) is as follows. Pore-forming (alpha) subunit of voltage-gated inwardly rectifying potassium channel (PubMed:10219239, PubMed:10753933, PubMed:10790218, PubMed:10837251, PubMed:11997281, PubMed:12063277, PubMed:18559421, PubMed:22314138, PubMed:22359612, PubMed:26363003, PubMed:27916661, PubMed:9230439, PubMed:9351446, PubMed:9765245). Channel properties are modulated by cAMP and subunit assembly (PubMed:10837251). Characterized by unusual gating kinetics by producing relatively small outward currents during membrane depolarization and large inward currents during subsequent repolarization which reflect a rapid inactivation during depolarization and quick recovery from inactivation but slow deactivation (closing) during repolarization (PubMed:10219239, PubMed:10753933, PubMed:10790218, PubMed:10837251, PubMed:11997281, PubMed:12063277, PubMed:18559421, PubMed:22314138, PubMed:22359612, PubMed:26363003, PubMed:27916661, PubMed:9230439, PubMed:9351446, PubMed:9765245). Forms a stable complex with KCNE1 or KCNE2, and that this heteromultimerization regulates inward rectifier potassium channel activity (PubMed:10219239, PubMed:9230439). {ECO:0000269|PubMed:10219239, ECO:0000269|PubMed:10753933, ECO:0000269|PubMed:10790218, ECO:0000269|PubMed:10837251, ECO:0000269|PubMed:11997281, ECO:0000269|PubMed:12063277, ECO:0000269|PubMed:18559421, ECO:0000269|PubMed:22314138, ECO:0000269|PubMed:22359612, ECO:0000269|PubMed:26363003, ECO:0000269|PubMed:27916661, ECO:0000269|PubMed:9230439, ECO:0000269|PubMed:9351446, ECO:0000269|PubMed:9765245}. [Isoform A-USO]: Has no inward rectifier potassium channel activity by itself, but modulates channel characteristics by forming heterotetramers with other isoforms which are retained intracellularly and undergo ubiquitin-dependent degradation. . [Isoform B-USO]: Has no inward rectifier potassium channel activity by itself, but modulates channel characteristics by forming heterotetramers with other isoforms which are retained intracellularly and undergo ubiquitin-dependent degradation. .