InterPro : IPR005408

Name  Two pore domain potassium channel, TWIK family Short Name  2pore_dom_K_chnl_TWIK
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.2P-domain channels influence the resting membrane potential and as a result can control cell excitability. In addition, they pass K+in response to changes in membrane potential, and are also tightly regulated by molecular oxygen, GABA (gamma-aminobutyric acid), noradrenaline and serotonin.The first member of this family (TOK1), cloned from Saccharomyces cerevisiae[], ispredicted to have eight potential transmembrane (TM) helices. However,subsequently-cloned two P-domain family members from Drosophila andmammalian species are predicted to have only four TM segments. They areusually referred to as TWIK-related channels (Tandem of P-domains in a Weakly Inward rectifying K+ channel) [, , , ]. Functional characterisation of these channels has revealed a diversity of properties in that they may show inward or outward rectification, their activity may be modulated in different directions by protein phosphorylation, and their sensitivity to changes in intracellular or extracellular pH varies. Despite these disparate properties, they are all thought to share the same topology offour TM segments, including two P-domains. That TWIK-related K+ channelsall produce instantaneous and non-inactivating K+ currents, which do notdisplay a voltage-dependent activation threshold, suggests that they arebackground (leak) K+ channels involved in the generation and modulation of the resting membrane potential in various cell types. Further studies have revealed that they may be found in many species, including: plants, invertebrates and mammals.
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Proteins

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2 Child Features

Id Name Short Name Type
IPR001779 Two pore domain potassium channel, TWIK-1 2pore_dom_K_chnl_TWIK1 Family
IPR005409 Two pore domain potassium channel, TWIK-2 2pore_dom_K_chnl_TWIK2 Family

1 Contains

Id Name Short Name Type
IPR013099 Two pore domain potassium channel domain 2pore_dom_K_chnl_dom Domain

0 Found In

0 Parent Features

12 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
Lesage F TWIK-1, a ubiquitous human weakly inward rectifying K+ channel with a novel structure. 1996 EMBO J 15 1004-11
Fink M Cloning, functional expression and brain localization of a novel unconventional outward rectifier K+ channel. 1996 EMBO J 15 6854-62
Duprat F TASK, a human background K+ channel to sense external pH variations near physiological pH. 1997 EMBO J 16 5464-71
Ketchum KA A new family of outwardly rectifying potassium channel proteins with two pore domains in tandem. 1995 Nature 376 690-5
Goldstein SA ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae. 1996 Proc Natl Acad Sci U S A 93 13256-61



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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)