HOMOLOGS OF THE SYNAPTOBREVIN VAMP FAMILY OF SYNAPTIC VESICLE PROTEINS FUNCTION ON THE LATE SECRETORY PATHWAY IN SACCHAROMYCES-CEREVISIAE

The yeast S. cerevisiae possesses two genes, SNC1 and SNC2, that encod e homologs of vertebrate synaptic vesicle-associated membrane proteins , also known as synaptobrevins. Here we describe the cloning of SNC2 a nd demonstrate that yeast lacking both SNC genes are deficient in norm al bulk secretion, accumulate large numbers of post-Golgi vesicles, an d 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 pla ce the Snc proteins on the late secretory pathway in S. cerevisiae and provide direct in vivo evidence that synaptobrevin-like proteins medi ate the targeting and transport of secretory proteins.