voltage-gated potassium channel alpha subunit PIRSF:PIRSF002449 fam:Kchan_sub-a A voltage-gated potassium channel protein that has a core domain composition consisting of six transmembrane domains (S1-S6), arranged in a voltage sensor (S1-S4) and pore modules (S5-P-S6), and with both N and C termini on the intracellular side of the membrane. The charged S4 segment with a basic amino acid at every third position confers their voltage sensitivity. A hallmark of this class is the presence of an N-terminal K+ channel tetramerisation domain (Pfam:PF02214) (T1), which encodes molecular determinants for subfamily-specific assembly of alpha-subunits into functional tetrameric channels. Carbonyl oxygen atoms from the potassium channel signature sequence (TTxGYGD) line the selectivity filter, where they preferentially coordinate potassium. Voltage-gated potassium channels are composed of tetramers of alpha subunits with each alpha subunit containing a voltage sensor and contributing to the central pore. This pore is formed by these subunits that encircle a central ion conduction pathway. Category=family. protein PR:000000685 voltage-gated potassium channel protein