THE SYNAPTOBREVIN-RELATED DOMAINS OF BOS1P AND SEC22P BIND TO THE SYNTAXIN-LIKE REGION OF SED5P

SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment p rotein receptors) ape cytoplasmically oriented membrane proteins that reside on vesicular carriers (V-SNARE) and target organelles (t-SNARE) . The pairing of a stage-specific v-SNARE with its cognate t-SNARE may mediate the specificity of membrane traffic. In the yeast Saccharomyc es cerevisiae transport between the endoplasmic reticulum and Golgi co mplex employs two v-SNAREs, Bos1p and Sec22p, each containing a domain that is related to the neuronal v-SNARE synaptobrevin, Sed5p, which i s homologous to syntaxin, is the t-SNARE that functions at this stage of the secretory pathway. Here we report that, regions of Bos1p and Se c22p, which are homologous to synaptobrevin, bind to the syntaxin-like domain of Sed5p, Furthermore, we demonstrate that efficient v-SNARE/t -SNARE interactions require the participation of both v-SNAREs, indica ting that, unlike post-Golgi membrane traffic, the active form of the endoplasmic reticulum to Golgi V-SNARE is a heteromeric complex.