ASSEMBLY AND DISASSEMBLY OF A TERNARY COMPLEX OF SYNAPTOBREVIN, SYNTAXIN, AND SNAP-25 IN THE MEMBRANE OF SYNAPTIC VESICLES

The synaptic membrane proteins synaptobrevin, syntaxin, and SNAP-25 fo rm a ternary complex that can be disassembled by the ATPase N-ethylmal eimide-sensitive factor (NSF) in the presence of soluble cofactors (SN AP proteins). These steps are thought to represent molecular events in volved in docking and subsequent exocytosis of synaptic vesicles. Usin g two independent and complementary approaches, we now report that suc h ternary complexes form in the membrane of highly purified and monodi sperse synaptic vesicles in the absence of the plasma membrane. Furthe rmore, the complexes are reversibly dissociated by NSF and SNAP protei ns. Thus, ternary complexes can be assembled and disassembled while al l three proteins are anchored as neighbors in the same membrane, sugge sting that NSF is involved in priming synaptic vesicles for exocytosis .