TY - JOUR T1 - Characterization of the omega-conotoxin-binding molecule in rat brain synaptosomes and cultured neurons. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 87 LP - 90 VL - 34 IS - 2 AU - B Marqueze AU - N Martin-Moutot AU - C Levêque AU - F Couraud Y1 - 1988/08/01 UR - http://molpharm.aspetjournals.org/content/34/2/87.abstract N2 - omega-Conotoxin GVIA is a peptide purified from the venom of the marine snail, Conus geographus, that specifically blocks voltage-sensitive calcium channels in neurons. A mono-[125I]iodo-omega-conotoxin was prepared and specific binding to both rat brain synaptosomal membranes and cultured neurons was detected. The interaction was irreversible and the association kinetic constant k was measured at 5-7 X 10(6) M-1 s-1 in synaptosomes and at 2-4 X 10(6) M-1 s-1 on intact neurons. The binding site capacities were 650 and 60 fmol/mg of protein, respectively. No competition was detected with other calcium channel blockers or with toxins acting on Na+ or K+ channels but the binding was lowered by the divalent cations Co2+ and Ca2+. Photoaffinity experiments specifically labeled a single component with an apparent Mr of 222,000 +/- 7,000 in brain synaptosomes and 245,000-300,000 in cultured embryonic neurons. ER -