BET1P ACTIVATES THE V-SNARE BOS1P

Bet1p is a type II membrane protein that is required for vesicular tra nsport between the endoplasmic reticulum and Golgi complex in the yeas t Saccharomyces cerevisiae. A domain of Bet1p, that shows potential to be involved in a coiled-coil interaction, is homologous to a region o f the neuronal protein SNAP-25. Here, we used in vitro binding studies to demonstrate that Bet1p plays a role in potentiating soluble NSF at tachment protein receptor (SNARE) interactions. Mutational analysis po ints to the coiled-coil region as necessary for Bet1p function, and ci rcular dichroism experiments support this theory. In vitro binding stu dies were also used to demonstrate that a direct interaction between B et1p and Bos1p is required for the efficient interaction of the vesicl e SNARE with its SNARE target. Genetic studies suggest that the intera ctions of Bet1p with Bos1p are regulated by the small GTP-binding prot ein Ypt1p.