Presynaptic alpha-latrotoxin receptor components interact with protein p65 of synaptic vesicle membranes.

Purified preparations of bovine brain alpha-latrotoxin receptor contain proteins of 39 kDa and 65 kDa. Sequence analysis shows that the 65 kDa protein corresponds to p65, a synaptic vesicle membrane protein previously identified in rat synaptic vesicles, and that the 39 kDa protein is a proteolytic fragment of the 65 kDa protein. The 39 kDa and 65 kDa proteins appear in receptor samples because of their specific interaction with components of the alpha-latrotoxin receptor. This interaction may represent an essential step in perfusion and/or the fusion of synaptic vesicle membranes with the plasma membrane of the presynaptic terminal, both of which are final steps in the exocytosis of neurotransmitters.