Calcium channel antagonist omega-conotoxin binds to intramembrane particles of isolated nerve terminals.
Voltage-sensitive calcium channels play a key role in evoked neurotransmitter release and their distribution in presynaptic membranes can be critical for fast signalling at chemical synapses. Using a biotinylated derivative of the neuronal calcium channel antagonist, omega-conotoxin, and a combination of colloidal gold labeling and freeze-fracture techniques, we have labeled calcium channels present at the membrane of nerve terminals isolated from the electric organ of Torpedo marmorata. The biotinylated blocker exerts an inhibitory action on the high potassium-evoked release of adenosine triphosphate as the native toxin does and its interaction with biological membranes is specific as shown in displacement experiments. This study shows that an antagonist specific for voltage-activated calcium channels binds to intramembrane particles in presynaptic membranes, reinforcing the idea that these particles, concentrated at neurotransmitter release sites, effectively represent calcium channels.
Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Hospital de Bellvitge, Universitat de Barcelona, Spain.
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Fariñas
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Egea
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Blasi
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Cases
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Marsal
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins; D002121:Calcium Channel Blockers / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004557:Electric Organ / Q000294:innervation / Q000378:metabolism; D005614:Freeze Fracturing; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000378:metabolism* / Q000648:ultrastructure; D010455:Peptides / Q000378:metabolism*; D019809:Streptavidin; D013347:Subcellular Fractions / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism / Q000648:ultrastructure; D014101:Torpedo / Q000502:physiology*; D020866:omega-Conotoxin GVIA
D001426:Bacterial Proteins; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D000255:Adenosine Triphosphate; D019809:Streptavidin; D020866:omega-Conotoxin GVIA