Vesicle-associated membrane protein and synaptophysin are associated on the synaptic vesicle

The synaptic vesicle membrane protein VAMP (vesicle-associated membrane protein or synaptobrevin) has been implicated in synaptic vesicle docking and fusion. Synaptophsin (p38), also a synaptic vesicle membrane protein, has four transmembrane domains and may function as a gap junction-like pore or channel. Here we report evidence for a direct interaction between VAMP and synaptophysin using chemical cross-linking followed by the identification of immunoreactive protein complexes. A prominent complex of 56 kDa was found to consist of VAMP and synaptophysin. Furthermore, we demonstrate that this VAMP-synaptophysin complex is enriched in the synaptic vesicle fraction of rat brain, is independent of detergent solubilization, and is present in PC12 cells subjected to in vivo cross-linking.