Purified omega-conotoxin GVIA receptor of rat brain resembles a dihydropyridine-sensitive L-type calcium channel.

The omega-conotoxin GVIA (CTX) receptor has been purified 1900-fold to apparent homogeneity by monitoring both reversible binding of 125I-labeled CTX (125I-CTX) and photoincorporation of N-hydroxysuccinimidyl-4-azidobenzoate-125I-CTX (HSA-125I-CTX). Photoincorporation of HSA-125I-CTX into a 230-kDa protein exhibits a pharmacologic and chromatographic profile indicating that the 230-kDa protein is the CTX-binding subunit of the receptor. The pharmacologic specificity of 125I-CTX binding to the purified CTX receptor closely resembles that of the native membrane-bound form with respect to sensitivity towards CTX (Kd = 32 pM) and other peptide toxin antagonists. The purified CTX receptor comprises the 230-kDa protein (alpha 1) and four additional proteins with apparent molecular masses of 140 (alpha 2), 110, 70 (beta 2), and 60 (beta 1) kDa. This subunit structure closely resembles that of the 1,4-dihydropyridine-sensitive L-type calcium channel.