InterPro : IPR015449

Name  Potassium channel, calcium-activated, SK Short Name  K_chnl_Ca-activ_SK
Type  Family Description  Potassium channels are the most diverse group of the ion channel family[, ]. They are important in shaping the action potential, and in neuronal excitability and plasticity []. The potassium channel family iscomposed of several functionally distinct isoforms, which can be broadlyseparated into 2 groups []: the practically non-inactivating 'delayed' group and the rapidly inactivating 'transient' group.These are all highly similar proteins, with only small amino acidchanges causing the diversity of the voltage-dependent gating mechanism,channel conductance and toxin binding properties. Each type of K+channel is activated by different signals and conditions depending on their type of regulation: some open in response to depolarisation of the plasma membrane; others in response to hyperpolarisation or an increase in intracellular calcium concentration; some can be regulated by binding of a transmitter, together with intracellular kinases; while others are regulated by GTP-binding proteins orother second messengers []. In eukaryotic cells, K+channelsare involved in neural signalling and generation of the cardiac rhythm, act as effectors in signal transduction pathways involving G protein-coupled receptors (GPCRs) and may have a role in target cell lysis by cytotoxic T-lymphocytes []. In prokaryotic cells, they play a role in themaintenance of ionic homeostasis [].All K+channels discovered so far possess a core of alpha subunits, each comprising either one or two copies of a highly conserved pore loop domain (P-domain). The P-domain contains the sequence (T/SxxTxGxG), which hasbeen termed the K+selectivity sequence.In families that contain one P-domain, four subunits assemble to form a selective pathway for K+across the membrane.However, it remains unclear how the 2 P-domain subunits assemble to form a selective pore. The functional diversity of these families can arise through homo- or hetero-associations of alpha subunits or association with auxiliary cytoplasmic beta subunits. K+channel subunits containing one pore domain can be assigned into one of two superfamilies: those that possess six transmembrane (TM) domains and those that possess only two TM domains.The six TM domain superfamily can be further subdivided into conserved gene families: the voltage-gated (Kv) channels; the KCNQ channels (originally known as KvLQT channels); the EAG-like K+channels; and three types of calcium (Ca)-activated K+channels (BK, IK and SK)[]. The 2TM domain family comprises inward-rectifying K+channels. In addition, there are K+channel alpha-subunits that possess two P-domains. These are usually highly regulated K+selective leak channels.Ca2+-activated K+ channels are a diverse group of channels that are activated by an increase in intracellular Ca2+ concentration. They are found in the majority of nerve cells, where they modulate cell excitability and action potential. Three types of Ca2+-activated K+ channel have been characterised, termed small-conductance (SK), intermediate conductance (IK) and large conductance (BK) respectively [].SK channels are thought to play an important role in the functioning of all excitable tissues. To date, 3 subtypes (designated SK1-SK3) have been cloned, each of which possesses a different tissue expression profile: SK1 channels are expressed in the heart; SK2 channels are found in the adrenal gland; and SK3 channels are known to be present in skeletal muscle []. SK channels have a single-channel conductance of 2-20 pS and are activated by rises in cytosolic calcium with half maximal activation in the 400-800 nM range [, ]. Unlike BK channels, they are voltage insensitive and unaffected by low concentrations of TEA, charybdotoxin, or iberiotoxin. However, they are potently blocked by the bee venom apamin [, ], tubocurarine, and quaternary salts of bicuculline [, ]. A new series of compounds that block SK channels include dequalinium

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

2 Contains

Id Name Short Name Type
IPR004178 Calmodulin-binding domain CaM-bd_dom Domain
IPR013099 Two pore domain potassium channel domain 2pore_dom_K_chnl_dom Domain

0 Found In

0 Parent Features

15 Publications

First Author Title Year Journal Volume Pages
Perney TM The molecular biology of K+ channels. 1991 Curr Opin Cell Biol 3 663-70
Luneau C Shaw-like rat brain potassium channel cDNA's with divergent 3' ends. 1991 FEBS Lett 288 163-7
Attali B Cloning, functional expression, and regulation of two K+ channels in human T lymphocytes. 1992 J Biol Chem 267 8650-7
Schwarz TL Multiple potassium-channel components are produced by alternative splicing at the Shaker locus in Drosophila. 1988 Nature 331 137-42
Tempel BL Cloning of a probable potassium channel gene from mouse brain. 1988 Nature 332 837-9
Stühmer W Molecular basis of functional diversity of voltage-gated potassium channels in mammalian brain. 1989 EMBO J 8 3235-44
Miller C An overview of the potassium channel family. 2000 Genome Biol 1 REVIEWS0004
Vergara C Calcium-activated potassium channels. 1998 Curr Opin Neurobiol 8 321-9
Blatz AL Quantitative description of three modes of activity of fast chloride channels from rat skeletal muscle. 1986 J Physiol 378 141-74
Tseng-Crank J Cloning, expression, and distribution of functionally distinct Ca(2+)-activated K+ channel isoforms from human brain. 1994 Neuron 13 1315-30
Romey G Apamin: a specific toxin to study a class of Ca2+-dependent K+ channels. 1984 J Physiol (Paris) 79 259-64
Blatz AL Single apamin-blocked Ca-activated K+ channels of small conductance in cultured rat skeletal muscle. 1986 Nature 323 718-20
Johnson SW Bicuculline methiodide potentiates NMDA-dependent burst firing in rat dopamine neurons by blocking apamin-sensitive Ca2+-activated K+ currents. 1997 Neurosci Lett 231 13-6
Seutin V Recent advances in the pharmacology of quaternary salts of bicuculline. 1999 Trends Pharmacol Sci 20 268-70
Köhler M Small-conductance, calcium-activated potassium channels from mammalian brain. 1996 Science 273 1709-14

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Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)