Calcium Channel, Voltage Dependent, Beta 3 Subunit (CACNb3)

Collin et al. (1994) isolated the beta subunit of a human voltage-dependent calcium channel gene from a 9-week-old human total-embryo cDNA library. The gene encodes a 482-amino acid polypeptide with a predicted mass of 54,571 kD. CACNb3 was expressed mostly in brain, smooth muscle, and ovary. The structures showed that the beta subunit core contains 2 interacting domains: a Src homology 3 (SH3) domain and a guanylate kinase domain. The AID binds to a hydrophobic groove in the guanylate kinase domain through extensive interactions, conferring extremely high affinity between alpha-1 and beta subunits. The beta-interaction domain (BID) is essential both for the structural integrity of and for bridging the SH3 and guanylate kinase domains, but it does not participate directly in binding alpha-1.