May play a role in vesicular transport from endoplasmic reticulum to Golgi. Part of the multisubunit TRAPP (transport protein particle) complex. Belongs to the TRAPP small subunits family. BET5 subfamily. The gene for this protein is duplicated in strains AX3 and AX4. These strains contain a duplication of a segment of 750 kb of chromosome 2 compared to the corresponding sequence in strain AX2.