Identification and characterization of five new subunits of TRAPP.

TRAPP (transport protein particle), a multiprotein complex containing ten subunits, plays a key role in the late stages of endoplasmic reticulum to Golgi traffic in the yeast Saccharomyces cerevisiae. We previously described the identification of five TRAPP subunits (Bet5p, Trs20p, Bet3p, Trs23p and Trs33p). Now we report the identification of the remaining five subunits (Trs31p, Trs65p, Trs85p, Trs120p and Trs130p) as well as an initial characterization of the yeast complex and its human homologue. We find that three of the subunits are dispensable for growth and a novel sequence motif is found in Bet3p, Trs31p and Trs33p. Furthermore, biochemical characterization of both yeast and human TRAPP suggests that this complex is anchored to a Triton X-100 resistant fraction of the Golgi. Differences between yeast and human TRAPP as well as the relationship of TRAPP subunits to other docking/tethering factors are discussed.