The correct targeting and fusion of vesicles is critical for the establishment and maintenance of organelles in the secretory pathway. In the Golgi complex, the protein p115 helps to target transport vesicles by promoting an interaction between two Golgin proteins: giantin on the transport vesicle and GM130 on the Golgi cisternal membranes. Using a cell-free system to look at Golgi membrane reassembly (as occurs after mitosis), Shorter et al. show that, in addition to promoting the long-range targeting activity of the Golgins, p115 also stimulates the subsequent protein interactions (underlying vesicle fusion) between a vesicle SNARE and a Golgi target SNARE. Furthermore, p115 contains a sequence motif that relates it to the SNAREs and that is important in promoting the SNARE interaction. Thus, the p115-induced transfer from long tethers (Golgins) to short tethers (SNAREs) may be critical in maintaining fidelity in membrane traffic.—SMH
J. Cell Biol. 157, 45 (2002).