Ca+2-activated K+ channel subunit beta-4; BK channel subunit beta-4; BKbeta4; Hbeta4; Ca+2-activated K+ channel, subfamily M subunit beta-4; charybdotoxin receptor subunit beta-4; K(VCA)beta-4; Maxi K channel subunit beta-4; Slo-beta-4 (KCNMB4)
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Function
- regulatory subunit of the Ca+2-activated K+ channel KCNMA1
- modulates the Ca+2 sensitivity & gating kinetics of KCNMA1, thus contributing to KCNMA1 channel diversity
- decreases the gating kinetics & Ca+2 sensitivity of the KCNMA1 channel, but with fast deactivation kinetics
- may decrease KCNMA1 channel openings at low Ca+2 but increases channel openings at high Ca+2
- renders KCNMA1 channel resistant to 100 nM charybdotoxin (CTX)
- phosphorylation modulates its effect on KCNMA1 activation kinetics
- interacts with KCNMA1 tetramer
- there are probably 4 molecules of KCMNB4 per KCNMA1 tetramer
Structure
- N-glycosylated
- a highly glycosylated form is promoted by KCNMA1
- glycosylation
- not required for interaction with KCNMA1 & subcellular location
- increases protection against charybdotoxin
- resistance to charybdotoxin (CTX) toxin is mediated by the extracellular domain
- belongs to the KCNMB (TC 8.A.14.1) family, KCNMB4 subfamily
Compartment
membrane
Expression
- predominantly expressed in brain
- in brain, expressed in cerebellum, cerebral cortex, medulla oblongata, spinal cord, occipital pole, frontal lobe, temporal lobe, putamen, amygdala, caudate nucleus, corpus callosum, hippocampus, substantia nigra & thalamus
- weakly expressed or not expressed in other tissues
Notes
- treatment with okadaic acid reduces its effect on KCNMA1