The domain within your query sequence starts at position 270 and ends at position 383; the E-value for the SK_channel domain shown below is 3.1e-51.



PFAM accession number:PF03530
Interpro abstract (IPR015449):

Potassium channels are the most diverse group of the ion channel family [(PUBMED:1772658), (PUBMED:1879548)]. They are important in shaping the action potential, and in neuronal excitability and plasticity [(PUBMED:2451788)]. The potassium channel family is composed of several functionally distinct isoforms, which can be broadly separated into 2 groups [(PUBMED:2555158)]: the practically non-inactivating 'delayed' group and the rapidly inactivating 'transient' group.

These are all highly similar proteins, with only small amino acid changes 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 or other second messengers [(PUBMED:2448635)]. In eukaryotic cells, K+ channels are 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 [(PUBMED:1373731)]. In prokaryotic cells, they play a role in the maintenance of ionic homeostasis [(PUBMED:11178249)].

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 has been 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) [(PUBMED:11178249)]. 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 [(PUBMED:9687354)].

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 [(PUBMED:8781233)]. 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 [(PUBMED:2432249), (PUBMED:7993625)]. 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 [(PUBMED:6099412), (PUBMED:2430185)], tubocurarine, and quaternary salts of bicuculline [(PUBMED:9280156), (PUBMED:10390643)]. A new series of compounds that block SK channels include dequalinium

GO process:potassium ion transport (GO:0006813)
GO component:integral component of membrane (GO:0016021)
GO function:small conductance calcium-activated potassium channel activity (GO:0016286)

This is a PFAM domain. For full annotation and more information, please see the PFAM entry SK_channel