Calcium-activated potassium channel

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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. However, 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.

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_Ca1.1 (BK, Slo1, Maxi-K, KCNMA1)
- Beta subunits: β1, β2, β3, β4

SK channel

K_Ca2.1 (SK1, KCNN1)
K_Ca2.2 (SK2, KCNN2)
K_Ca2.3 (SK3, KCNN3)

IK channel

K_Ca3.1 (IKCa1, SK4, KCNN4)

Other subfamilies

K_Ca4.1 (KCNT1)
K_Ca4.2 (SLICK, Slo2.1, KCNT2)
K_Ca5.1 (Slo3, KCNU1)

References

↑ 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.

External links

Calcium-Activated Potassium Channels at the US National Library of Medicine Medical Subject Headings (MeSH)
"Calcium-Activated Potassium Channels". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.

Membrane transport protein: ion channels (TC 1A)

Ca²⁺: Calcium channel

Ligand-gated	Inositol trisphosphate receptor 1 2 3 Ryanodine receptor 1 2 3

Voltage-gated	L-type/Ca_vα 1.1 1.2 1.3 1.4 N-type/Ca_vα2.2 P-type/Ca_vα 2.1 Q-type/Ca_vα2.1 R-type/Ca_vα2.3 T-type/Ca_vα 3.1 3.2 3.3 α₂δ-subunits 1 2 β-subunits β1 β2 β3 β4 γ-subunits γ1 γ2 γ3 γ4 Cation channels of sperm 1 2 3 4 Two-pore channel 1 2

Na⁺: Sodium channel

Constitutively active	Epithelial sodium channel α β γ δ

Proton-gated	Amiloride-sensitive cation channel 1 2 3 4

Voltage-gated	Na_vα 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 7A Na_vβ 1 2 3 4

K⁺: Potassium channel

Calcium-activated	BK channel α1 β1 β2 β3 β4 SK channel SK1 SK2 SK3 IK channel IK1 K_Ca 1.1 2.1 2.2 2.3 3.1 4.1 4.2 5.1

Inward-rectifier	K_ATP K_ir 1.1 2.1 2.2 2.3 2.4 2.6 GIRK/K_ir 3.1 3.2 3.3 3.4 K_ir 4.1 4.2 5.1 6.1 6.2 7.1

Tandem pore domain	K2P 1 2 3 4 5 6 7 9 10 12 13 15 16 17 18

Voltage-gated	K_vα1-6 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2.1 2.2 3.1 3.2 3.3 3.4 4.1 4.2 4.3 5.1 6.1 6.2 6.3 6.4 K_vα7-12 7.1 7.2 7.3 7.4 7.5 8.1 8.2 9.1 9.2 9.3 10.1 10.2 11.1/hERG 11.2 11.3 12.1 12.2 12.3 K_vβ 1 2 3 KCNIP 1 2 3 4 minK/ISK minK/ISK-like MiRP 1 2 3 Shaker gene

Miscellaneous

Cl^-: Chloride channel	ANO1 Bestrophin 1 2 CFTR CLCA 1 2 3 4 CLCN 1 2 3 4 5 6 7 KA KB CLIC 1 2 3 4 5 6 L1 CLNS 1A 1B

H⁺: Proton channel	HVCN1

M⁺: CNG cation channel	α 1 2 3 4 β 1 2 3 HCN FC 1 2 3 4

M⁺: TRP cation channel	TRPA (1) TRPC 1 2 3 4 4AP 5 6 7 TRPM 1 2 3 4 5 6 7 8 TRPML 1 2 3 TRPN TRPP 1 2 TRPV 1 2 3 4 5 6

H₂O (+ solutes): Porin	Aquaporin 0 1 2 3 4 5 6 7 8 9 Voltage-dependent anion channel 1 2 3 General bacterial porin family

Cytoplasm: Gap junction	Connexin: A GJA1 GJA3 GJA4 GJA5 GJA8 GJA9 GJA10 B GJB1 GJB2 GJB3 GJB4 GJB5 GJB6 GJB7 C GJC1 GJC2 GJC3 D GJD2 GJD3 GJD4) Innexin

By gating mechanism

Ion channel class	Ligand-gated Light-gated Voltage-gated Stretch-activated

see also disorders
B memb: cead, trns (1A, 1C, 1F, 2A, 3A1, 3A2-3, 3D), other

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