The following text describes a protein:
Function:
Pore-forming subunit of the voltage-gated potassium (Kv) channel involved in the regulation of cardiomyocyte excitability and important in normal development and functions of myocardium, inner ear, stomach and colon (By similarity). Associates with KCNE beta subunits that modulates current kinetics (By similarity). Induces a voltage-dependent by rapidly activating and slowly deactivating potassium-selective outward current (By similarity). Also promotes a delayed voltage activated potassium current showing outward rectification characteristic (By similarity). During beta-adrenergic receptor stimulation participates in cardiac repolarization by associating with KCNE1 to form the I(Ks) cardiac potassium current that increases the amplitude and slows down the activation kinetics of outward potassium current I(Ks) (By similarity). Muscarinic agonist oxotremorine-M strongly suppresses KCNQ1/KCNE1 current (By similarity). When associated with KCNE3, forms the potassium channel that is important for cyclic AMP-stimulated intestinal secretion of chloride ions (By similarity). This interaction with KCNE3 is reduced by 17beta-estradiol, resulting in the reduction of currents (By similarity). During conditions of increased substrate load, maintains the driving force for proximal tubular and intestinal sodium ions absorption, gastric acid secretion, and cAMP-induced jejunal chloride ions secretion (By similarity). Allows the provision of potassium ions to the luminal membrane of the secretory canaliculus in the resting state as well as during stimulated acid secretion (By similarity). When associated with KCNE2, forms a heterooligomer complex leading to currents with an apparently instantaneous activation, a rapid deactivation process and a linear current-voltage relationship and decreases the amplitude of the outward current (By similarity). When associated with KCNE4, inhibits voltage-gated potassium channel activity (By similarity). When associated with KCNE5, this complex only conducts current upon strong and continued depolarization (By similarity). Also forms a heterotetramer with KCNQ5 that has a voltage-gated potassium channel activity (By similarity). Binds with phosphatidylinositol 4,5-bisphosphate (By similarity). KCNQ1-KCNE2 channel associates with Na(+)-coupled myo-inositol symporter in the apical membrane of choroid plexus epithelium and regulates the myo-inositol gradient between blood and cerebrospinal fluid with an impact on neuron excitability.
Subcellular Localization:
Cell membrane; Multi-pass membrane protein. Cytoplasmic vesicle membrane. Early endosome. Membrane raft. Endoplasmic reticulum. Basolateral cell membrane. Apical cell membrane; Multi-pass membrane protein. Note=Colocalized with KCNE3 at the plasma membrane. Upon 17beta-oestradiol treatment, colocalizes with RAB5A at early endosome. Heterotetramer with KCNQ5 is highly retained at the endoplasmic reticulum and is localized outside of lipid raft microdomains. During the early stages of epithelial cell polarization induced by the calcium switch it is removed from the plasma membrane to the endoplasmic reticulum, where it is retained, and redistributed to the basolateral cell surface in a PI3K-dependent manner at a later stage. Colocalizes with SLC5A3 at the apical membrane of choroid plexus epithelium (By similarity).
Domain:
Each channel subunit contains six transmembrane segments (S1-S6) with S1-S4 forming one voltage sensing domain (VSD) and S5-S6 contributing to form one quarter of an interlocking pore-forming domain (PD); The segment S6 is involved in the inhibition of voltage-gated potassium channel activity by KCNE4; The CALM binding domains correspond to the first two membrane-proximal helical regions that interact with a single calmodulin/CALM molecule forming a clamp-like structure. Binding of CALM C-terminus to the first helix is calcium-independent and is essential for assembly of the structure. Binding of CALM N-terminus to the second helix is calcium-dependent and regulates electrophysiological activity of the channel; The C-terminal assembly domain carries the major determinants of tetramerization and subunit assembly specificity. Its coiled-coil region is four-stranded.
Sequence:
MAAASTPPRAERKRXSWSRLPGAQRESAGLAKKCPFSLELAESGPPSSALYAPVSPPSAPEPAPPASPASPAPPAADQGPQPPVSLDPRVSIYSVRRPLLARTHIQGRVYNFLERPTGWKCFAYHFTVFLIVLVCLIFSVLSTIEQYATLATGTLFWMEIVLVVFFGTEYVVRLWSAGCRSKYVGLWGRLRFARKPISIIDLIVVVASMVVLCVGSKGQVFATSAIRGIRFLQILRMLHVDRQGGTWRLLGSVVFIHRQELITTLYIGFLGLIFSSYFVYLAEKDAVNESGRVEFGSYADALWWGVVTVTTIGYGDKVPQTWVGKTIASCFSVFAISFFALPAGILGSGFALKVQQKQRQKHFNRQIPAAASLIQTAWRCYAAENPDSATWKIYIRKPTRGHALLSPSPKPKKSAMVKKKKFKLDKDNGVSPGEKTLPVPQITCEPPEERRPDHFPVDSHDGSVRKSPALLEVSTPQFLRTNSFAEDLDLEGETLLAPITHVSQLREHHRATVKVIRRMQYFVAKKKFQQARKPYDVRDVIEQYSQGHLNLMVRIKELQRRLDQSIGKPSLFVPISEKSKDRGSNSIGARLNRVEDKVTQLDQRLVLIADMLQQLLALHQGRCHGGAHPAQARDGDPADPELFLPTYEQLTVPRRDPEEGS