A stable interaction between syntaxin 1a and synaptobrevin 2 mediated by their transmembrane domains

The proteins synaptobrevin (VAMP), SNAP-25 and syntaxin 1 are essential for neuronal esocytosis. They assemble into a stable ternary complex which is thought to initiate membrane fusion, In vitro, the transmembrane domains of syntaxin and synaptobrevin are not required for association. Here we repor t a novel interaction between synaptobrevin and syntaxin that requires the presence of the transmembrane domains. When co-reconstituted into liposomes , the proteins form a stable binary complex that cannot be disassembled by NSF and that is resistant to denaturation by SDS, Cleavage of synaptobrevin with tetanus toxin does not affect the interaction. Furthermore, the compl ex is formed when a truncated version of syntaxin is used that contains onl y 12 additional amino acid residues outside the membrane anchor. me conclud e that the interaction is mediated by the transmembrane domains, (C) 1999 F ederation of European Biochemical Societies.