Pore-forming (alpha) subunit of a voltage-gated delayed rectifier potassium channel (PubMed:9738473, PubMed:11943152, PubMed:10880439, PubMed:22732247, PubMed:25556795, PubMed:27325704, PubMed:27005320, PubMed:27618660). Channel properties are modulated by subunit assembly (PubMed:11943152). Mediates IK(NI) current in myoblasts (PubMed:9738473). Involved in the regulation of cell proliferation and differentiation, in particular adipogenic and osteogenic differentiation in bone marrow-derived mesenchymal stem cells (MSCs) (PubMed:23881642). Channel activity is inhibited by interaction with Ca(2+)-bound calmodulin (PubMed:10880439, PubMed:27325704, PubMed:27005320, PubMed:27618660). Interaction of a single pore-forming alpha subunit with a calmodulin chain is sufficient to promote channel closure (PubMed:10880439). Channel activity is not regulated by cyclic nucleotides (By similarity). Channel activity is inhibited by binding intracellular phosphatidylinositol-3,5-bisphosphate and phosphatidylinositol-4,5-bisphosphate (PIP2), but is not inhibited by phosphatidylinositol 4-phosphate (PubMed:27005320). Inhibited by the spider kappa-theraphotoxin-Aa1a and mu/kappa-theraphotoxin-Ap1a (PubMed:30149017). The potassium channel is composed of a homo- or heterotetrameric complex of pore-forming alpha subunits that can associate with modulating beta subunits. Heteromultimer with KCNH5/EAG2 (PubMed:11943152). Interacts with ALG10B (By similarity). Interacts with RABEP1 (By similarity). Interacts (via C-terminus) with CTTN (PubMed:23144454). Interacts (via C-terminal cytoplasmic region) with Ca(2+)-bound calmodulin (PubMed:10880439, PubMed:27325704, PubMed:27618660). Interacts with the spider kappa-theraphotoxin-Aa1a and mu/kappa-theraphotoxin-Ap1a (PubMed:30149017). Perinuclear KCNH1 is located to NPC-free islands. Highly expressed in brain and in myoblasts at the onset of fusion, but not in other tissues. Detected in HeLa (cervical carcinoma), SH-SY5Y (neuroblastoma) and MCF-7 (epithelial tumor) cells, but not in normal epithelial cells. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. The C-terminal region interacts with the cyclic nucleotide-binding domain and contributes to regulate channel gating. The PAS and PAC domain interact with the cyclic nucleotide-binding domain and contribute to the regulation of channel gating (PubMed:27325704). Calmodulin binding clamps together the PAS and PAC domain with the cyclic nucleotide-binding domain from a neighboring subunit and causes a conformation change that leads to channel closure. The cyclic nucleotide-binding domain lacks residues that are essential for nucleotide-binding and cannot bind cyclic nucleotides. Instead, residues from the C-terminal domain (the so-called intrinsic ligand) bind in the cavity that would be expected to bind cyclic nucleotides. Interaction with the C-terminal region hinders interaction with CALM and reduces the affinity for CALM. Channel activity is regulated via tyrosine phosphorylation/dephosphorylation by SRC and PTPN6 (PubMed:24587194). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the potassium channel family. H (Eag) (TC 1.A.1.20) subfamily. Kv10.1/KCNH1 sub-subfamily.