Homologs of the synaptobrevin/VAMP family of synaptic vesicle proteins function on the late secretory pathway in S. cerevisiae

The yeast S. cerevisiae possesses two genes, SNC1 and SNC2, that encode homologs of vertebrate synaptic vesicle-associated membrane proteins, also known as synaptobrevins. Here we describe the cloning of SNC2 and demonstrate that yeast lacking both SNC genes are deficient in normal bulk secretion, accumulate large numbers of post-Golgi vesicles, and display a variety of conditional lethal phenotypes. In addition, we show that yeast Snc proteins localize to post-Golgi transport vesicles that accumulate in a late-acting sec mutant. Our findings clearly place the Snc proteins on the late secretory pathway in S. cerevisiae and provide direct in vivo evidence that synaptobrevin-like proteins mediate the targeting and transport of secretory proteins.