TRAPP, A HIGHLY CONSERVED NOVEL COMPLEX ON THE CIS-GOLGI THAT MEDIATES VESICLE DOCKING AND FUSION

We previously identified BET3 by its genetic interactions with BET1, a gene whose SNARE-like product acts in endoplasmic reticulum (ER)-to-G olgi transport. To gain insight into the function of Bet3p, we added t hree c-myc tags to its C-terminus and immunopurified this protein fron t a clarified detergent extract. Here we report that Bet3p is a member of a large complex (similar to 800 kDa) that me call TRAPP (transport protein particle). We propose that TRAPP plays a key role in the targ eting and/or fusion of ER-to-Golgi transport vesicles with their accep tor compartment. The localization of Bet3p to the cis-Golgi complex, a s well as biochemical studies showing that Bet3p functions on this com partment, support this hypothesis. TRAPP contains at least nine other constituents, Ave of which have been identified and shown to be highly conserved novel proteins.