Figure 6

The TRAPPII complex may have evolved from bacterial PapD chaperone of the usher pili assembly pathway. Cartoon showing the bacterial and eukaryotic trafficking pathways guided by the PapD and TRAPPII complex, respectively. In bacteria, PapD functions as a chaperone that restrains and tethers the polypeptides to the PapC usher pore complex as they convey across the periplasm between the inner- and outer membrane [35]. In eukaryotes, the TRAPPII particle with its distinct Trs120, Trs130, and Trs65 components (yeast), as compared to the TRAPPI complex, targets proteins in late Golgi trafficking to the outer membrane. In metazoans a similar function of the TRAPPII complex is believed to traffic vesicular cargo to the plasma membrane and cilium [17]. TRAPPC8 may also be involved in Rabin8 centrosome targeting, but it is unclear whether TRAPPC8 functions together with or separately from the TRAPPII complex in this process.