Solubilized 125I-ω conotoxin MVIIC receptors from rat cerebellum were immunoprecipitated by antibodies directed against the calcium channel α1A subunit. Anti-αIA antibodies recognized a 240-220, 180 and 160 kDa proteins in immunoblots of cerebellar membranes. Disuccinimidyl suberate cross-linked 125I-ω conotoxin MVIIC to an α2δ-like 200-180 kDa subunit, which migrated at 150-140 kDa after disulfide reduction. These observations are consistent with a heteromeric structure in which high affinity ω conotoxin MVIIC binding sites formed by α1A subunits are located in close proximity to peripheral α2 subunits.
