TRAPP (TRAnsport Protein Particle) tethering complexes are involved in vesicle trafficking in the secretory pathway. In yeast, three TRAPP complexes (I-III) have been described. In mammals and Drosophila, two TRAPP complexes, TRAPPII and TRAPPIII, have been described which mediates ER-Golgi and intra-Golgi trafficking. TRAPP complexes possess Rab guanine nucleotide-exchange factor activity. (Adapted from FBrf0238107.)