Calcium-activated potassium channel

Calcium-activated potassium channels are divided into BK channels, IK channels, and SK channels based on their conductance (big, intermediate, and small conductance).

This family of ion channels is, for the most part, activated by intracellular Ca²⁺ and contains 8 members. It should be noted, however, that some of these channels (the K_Ca4 and K_Ca5 channels) are responsive instead to intracellular Na⁺ and Cl^-. Furthermore, the K_Ca1 family is both Ca²⁺ and voltage activated, further complicating the description of this family. The K_Ca channel α subunits have six transmembrane segments similar to the K_Vs, except K_Ca1, in which the N-terminus makes a seventh pass across the membrane to end up outside the cell. The α subunits make homo- and hetero-tetrameric complexes.

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Homology classification

Below is a list of the 8 known calcium-activated potassium channel grouped according to sequence homology of transmembrane hydrophobic cores:^[1]

BK channel

• K_ca1.x : K_ca1.1 (KCNMA1)

SK channel

• K_ca2.x : K_ca2.1 (KCNN1), K_ca2.2 (KCNN2), K_ca2.3 (KCNN3)
• K_ca3.x: K_ca3.1 (KCNN4)
• K_ca4.x: K_ca4.1 (KCNT1), K_ca4.2 (KCNT2)

IK channel

• K_ca5.x: K_ca5.1 (KCNMC1)

See also

• BK channel
• SK channel

References

1. ^ Wei AD, Gutman GA, Aldrich R, Chandy KG, Grissmer S, Wulff H (2005). "International Union of Pharmacology. LII. Nomenclature and molecular relationships of calcium-activated potassium channels.". Pharmacol Rev 57 (4): 463-72. doi:10.1124/pr.57.4.9. PMID 16382103.