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3  structures 64  species 0  interactions 170  sequences 5  architectures

Family: Potassium_chann (PF11404)

Summary: Potassium voltage-gated channel

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Potassium voltage-gated channel Provide feedback

Fast inactivation of voltage-dependant potassium channels occurs by a 'ball-and-chain'-type mechanism. It controls membrane excitability and signal propagation in central neurons [1]. Inactivation is regulated by protein phosphorylation where phosphorylation of serine residues leads to a reduction of the fast inactivation [1].

Literature references

  1. Antz C, Bauer T, Kalbacher H, Frank R, Covarrubias M, Kalbitzer HR, Ruppersberg JP, Baukrowitz T, Fakler B; , Nat Struct Biol. 1999;6:146-150.: Control of K+ channel gating by protein phosphorylation: structural switches of the inactivation gate. PUBMED:10048926 EPMC:10048926


This tab holds annotation information from the InterPro database.

InterPro entry IPR021105

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.

The Kv family can be divided into several subfamilies on the basis of sequence similarity and function. Four of these subfamilies, Kv1 (Shaker), Kv2 (Shab), Kv3 (Shaw) and Kv4 (Shal), consist of pore-forming alpha subunits that associate with different types of beta subunit. Each alpha subunit comprises six hydrophobic TM domains with a P-domain between the fifth and sixth, which partially resides in the membrane. The fourth TM domain has positively charged residues at every third residue and acts as a voltage sensor, which triggers the conformational change that opens the channel pore in response to a displacement in membrane potential [PUBMED:10712896]. More recently, 4 new electrically-silent alpha subunits have been cloned: Kv5 (KCNF), Kv6 (KCNG), Kv8 and Kv9 (KCNS). These subunits do not themselves possess any functional activity, but appear to form heteromeric channels with Kv2 subunits, and thus modulate Shab channel activity [PUBMED:9305895]. When highly expressed, they inhibit channel activity, but at lower levels show more specific modulatory actions.

A voltage-dependent potassium channel gene designated Shaw was initially isolated from Drosophila melanogaster (Fruit fly). Subsequently, several vetebrate potassium channels with similar amino acid sequences were found and, together with the D. melanogaster channel, now constitute the Kv3 family. These channels are thought to play a role in shortening of action potential durations and modulating pre-synaptic neurotransmitter release. In mammals, the family consists of 4 genes (Kv3.1, Kv3.2, Kv3.3 and Kv3.4). Each gene product has its own subcellular location and function.

Fast inactivation of voltage-dependent potassium channels controls membrane excitability and signal propagation in central neurons. This occurs by a 'ball-and-chain'-type mechanism where an N-terminal protein inactivation domain occludes the pore from the cytoplasmic side. In Kv3 channels this process is regulated by protein phosphorylation, where phosphorylation of serine residues leads to a reduction or removal of the fast inactivation [PUBMED:10048926].

Domain organisation

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Alignments

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(2)
Full
(170)
Representative proteomes UniProt
(258)
NCBI
(870)
Meta
(0)
RP15
(13)
RP35
(42)
RP55
(79)
RP75
(105)
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  Seed
(2)
Full
(170)
Representative proteomes UniProt
(258)
NCBI
(870)
Meta
(0)
RP15
(13)
RP35
(42)
RP55
(79)
RP75
(105)
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  Seed
(2)
Full
(170)
Representative proteomes UniProt
(258)
NCBI
(870)
Meta
(0)
RP15
(13)
RP35
(42)
RP55
(79)
RP75
(105)
Raw Stockholm Download   Download   Download   Download   Download   Download   Download   Download    
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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

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Trees

This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

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Curation View help on the curation process

Seed source: pdb_1b4g
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Pollington J , Finn RD
Number in seed: 2
Number in full: 170
Average length of the domain: 27.60 aa
Average identity of full alignment: 72 %
Average coverage of the sequence by the domain: 4.34 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 45638612 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.0 20.0
Trusted cut-off 21.1 20.1
Noise cut-off 19.7 19.9
Model length: 29
Family (HMM) version: 8
Download: download the raw HMM for this family

Species distribution

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Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Potassium_chann domain has been found. There are 3 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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