Purified dihydropyridine-sensitive calcium channels from rabbit transverse-tubule membranes consist of three noncovalently associated classes of subunits: a (167 kDa), p (54 kDa), and y (30 kDa). Cleavage of disulfide bonds reveals two distinct a polypeptides and an additional component, 6.The a, subunit, a 175-kDa polypeptide that is not N-glycosylated, contains the dihydropyridine binding site, cAMP-dependent protein kinase phosphorylation site(s), and substantial hydrophobic domain(s). a2, a 143-kDa glycoprotein, has none of the properties characteristic of al but binds lectins and contains about 25% N-linked carbohydrate. a2 is disulfidelinked to 6, a 24-to 27-kDa glycopeptide. .3 (54 kDa) contains a cAMP-dependent phosphorylation site but is not N-glycosylated and does not have a hydrophobic domain. y (30 kDa) has a carbohydrate content of about 30% and extensive hydrophobic domain(s). Precipitation with affinity-purifiled anti-a, antibodies or a2-specific lentil lectin-agarose demonstrated that aja213yS behaves as a complex in the presence of digitonin or 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, whereas the a26 complex dissociates from al.fy in the presence of Triton X-100. A model for subunit interaction and membrane insertion is proposed on the basis of these observations.