CHARACTERIZATION OF THE OMEGA-CONOTOXIN-BINDING MOLECULE IN RAT-BRAIN SYNAPTOSOMES AND CULTURED NEURONS

  • 1 August 1988
    • journal article
    • research article
    • Vol. 34  (2) , 87-90
Abstract
.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 .times. 106 M-1 s-1 in synaptosomes and at 2-4 .times. 106 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.