Characterization of the omega-conotoxin-binding molecule in rat brain synaptosomes and cultured neurons.
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.
Marqueze
B
B
Laboratoire de Biochimie, CNRS UA 1179, Faculté de Médecine Nord, Marseille, France.
Martin-Moutot
N
N
Levêque
C
C
Couraud
F
F
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D008978:Mollusk Venoms / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009498:Neurotoxins / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000378:metabolism; D020866:omega-Conotoxin GVIA
D007473:Ion Channels; D008565:Membrane Proteins; D008978:Mollusk Venoms; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D020866:omega-Conotoxin GVIA