Regulatory subunit of the voltage-gated calcium channel that gives rise to L-type calcium currents in skeletal muscle. Regulates channel inactivation kinetics. Component of a calcium channel complex consisting of a pore-forming alpha subunit (CACNA1S) and the ancillary subunits CACNB1 or CACNB2, CACNG1 and CACNA2D1 (PubMed:2158672, PubMed:12409298, PubMed:26680202, PubMed:27580036). The channel complex contains alpha, beta, gamma and delta subunits in a 1:1:1:1 ratio, i.e. it contains either CACNB1 or CACNB2 (PubMed:26680202, PubMed:27580036). Skeletal muscle (at protein level). N-glycosylated. Belongs to the PMP-22/EMP/MP20 family. CACNG subfamily.