Ca+2-activated K+ channel subunit beta-3; BK channel subunit beta-3; BKbeta3; Hbeta3; Ca+2-activated K+ channel, subfamily M subunit beta-3; charybdotoxin receptor subunit beta-3; K(VCA)beta-3; Maxi K channel subunit beta-3; Slo-beta-3 (KCNMB3, KCNMB2, KCNMBL)

Function

• regulatory subunit of the Ca+2-activated K+ channel KCNMA1
• modulates Ca+2 sensitivity & gating kinetics of KCNMA1, thus contributing to KCNMA1 channel diversity
• alters functional properties of the KCNMA1 channel current
• isoform 2, isoform 3 & isoform 4 partially inactivate the KCNBMA current
• isoform 4 induces a fast & incomplete inactivation of the KCNMA1 channel detectable only at large depolarizations
• in contrast, isoform 1 does not induce detectable inactivation of KCNMA1
• 2 or more subunits of KCNMB3 are required to block the KCNMA1 tetramer
• interacts with KCNMA1 tetramer
• there are probably 4 molecules of KCMNB3 per KCNMA1 tetramer

Structure

• N-glycosylated
• isoform 4 cytoplasmic N-terminus domain participates in the partial inactivation of KCNMA1, possibly by binding to a receptor site
• the extracellular domain contains disulfide bond essential for the gating mechanism
• the extracellular domain forms gates to block ion permeation, providing a mechanism by which current can be rapidly diminished upon cellular repolarization
• belongs to the KCNMB (TC 8.A.14.1) family, KCNMB3 subfamily

Compartment

membrane

Alternative splicing

named isoforms=4

Expression

• isoform 1, isoform 3 & isoform 4 are widely expressed
• isoform 2 is expressed placenta, pancreas, kidney & heart
• isoform 1 & isoform 3 are highly expressed in pancreas & testis

More general terms

• transmembrane 2 protein
• K+ channel subfamily M
• glycoprotein

Component of

• Ca+2-activated K+ channel

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=27094
• OMIM: https://mirror.omim.org/entry/605222
• UniProt: http://www.uniprot.org/uniprot/Q9NPA1.html