Component of the multisubunit TRAPP (transport protein particle) III complex (PubMed:28536105, PubMed:34229011). As a component of TRAPPIII complex, participates in the activation of RAB1 and RAB43, but not RAB11A, RAB11B, nor RAB19 (PubMed:28536105, PubMed:34229011). {ECO:0000269|PubMed:28536105, ECO:0000269|PubMed:34229011}. This is the function of TRAPPC13 (trafficking protein particle complex subunit 13, Ensembl gene identifier ENSG00000113597).