Pore-forming (alpha) subunit of voltage-gated potassium channel. Elicits a slowly activating, outward rectifying current. Channel properties may be modulated by cAMP and subunit assembly. The potassium channel is probably composed of a homo- or heterotetrameric complex of pore-forming alpha subunits that can associate with modulating beta subunits. Detected in superior cervical, mesenteric and coeliac ganglia. Expressed in brain (piriform cortex, olfactory tubercle, cerebral cortex, hippocampus pyramidial cells and dentate gyrus and basal ganglia of caudate/putamen and accumbens nucleus). Expressed in pituitary. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Belongs to the potassium channel family. H (Eag) (TC 1.A.1.20) subfamily. Kv12.1/KCNH8 sub-subfamily.