EVOLUTIONARY CONSERVATION OF SYNAPTOSOME-ASSOCIATED PROTEIN-25-KDA (SNAP-25) SHOWN BY DROSOPHILA AND TORPEDO CDNA CLONES

The neuron-specific proteins SNAP-25 (synaptosome-associated protein 2 5 kDa), synaptobrevin and syntaxin, are localized to presynaptic termi nals in mammals and have been found to associate with proteins involve d in vesicle docking and membrane fusion. We describe here SNAP-25 cDN A clones from the fruit fly Drosophila melanogaster and the ray Torped o marmorata. In situ hybridization showed that SNAP-25 mRNA is exclusi vely found in brain and ganglia in Drosophila with a pattern suggestin g expression in most neurons. The Drosophila and Torpedo proteins show 61 and 81% amino acid identity to mouse SNAP-25, a degree of conserva tion similar to that previously reported for synaptobrevin. None of th e SNAP-25 sequences has a membrane-spanning region, but all contain a cluster of cysteine residues that can be palmitoylated for membrane at tachment. SNAP-25 displays sequence similarity to syntaxin A and B. Th ese data show that SNAP-25 and synaptobrevin, which are both implicate d in vesicle docking and/or membrane fusion, have both been highly con served during evolution. This supports the existence of a basic molecu lar machinery for synaptic vesicle docking in vertebrate and invertebr ate synapses.