Potassium large conductance calcium-activated channel, subfamily M, alpha 1

Calcium-activated potassium channel subunit alpha-1 also known as potassium large conductance calcium-activated channel, subfamily M, alpha member 1 (KCa1.1) is a voltage gated is_associated_with::ion channel encoded by the KCNMA1 is_associated_with::gene.

Function
KCa1.1 channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the control of smooth muscle tone and neuronal excitability.

Structure
KCa1.1 channels have a tetrameric structure. Each monomer of the channel-forming alpha subunit is the product of the KCNMA1 gene. Modulatory beta subunits (encoded by is_associated_with::KCNMB1, is_associated_with::KCNMB2, is_associated_with::KCNMB3, or is_associated_with::KCNMB4) can associate with the tetrametic channel. Alternatively spliced transcript variants encoding different isoforms have been identified.

Each KCa1.1 channel alpha subunit consists of (from N- to C-terminal):
 * 1) A unique is_associated_with::transmembrane domain (S0) that precedes the 6 transmembrane domains (S1-S6) conserved in all voltage-dependent K+ channels.
 * 2) A voltage sensing domain (S1-S4).
 * 3) A K+ channel pore domain (S5, selectivity filter, and S6).
 * 4) A cytoplasmic C-terminal domain (CTD) consisting of a pair of RCK domains that assemble into an octameric gating ring on the intracellular side of the tetrameric channel.    The CTD contains four primary binding sites for Ca2+, called "calcium bowls", encoded within the second RCK domain of each monomer.

Available X-ray structures:
 * - Crystal Structure of the Human BK Gating Apparatus
 * - Structure of the Intracellular Gating Ring from the Human High-conductance Ca2+ gated K+ Channel (BK Channel)