Proceedings of the National Academy of Sciences of the United States of America
Intracellular membrane fusion requires R-SNAREs and Q-SNAREs to assemble into a four-helical parallel coiled-coil, with their hydrophobic anchors spanning the two apposed membranes. Based on the fusion properties of chemically defined SNARE- proteoliposomes, it has been proposed that the assembly of this helical bundle transduces force through the entire bilayer via the transmembrane SNARE anchor domains to drive fusion. However, an R-SNARE, Nyv1p, with a genetically engineered lipid anchor that spans half of the bilayer suffices for the fusion of isolated vacuoles, although this organelle has other R-SNAREs. To demonstrate unequivocally the fusion activity of lipid-anchored Nyv1p, we reconstituted proteoliposomes with purified lipid-anchored Nyv1p as the only protein. When these proteoliposomes were incubated with those bearing cognate Q-SNAREs, there was trans-SNARE complex assembly but, in accord with prior studies of the neuronal SNAREs, little lipid mixing. However, the addition of physiological fusion accessory proteins (HOPS, Sec17p, and Sec18p) allows lipid-anchored Nyv1p to support fusion, suggesting that trans-SNARE complex function is not limited to force transduction across the bilayers through the transmembrane domains.
Xu, Hao; Zick, Michael; Wickner, William T.; and Jun, Youngsoo, "A Lipid-Anchored SNARE Supports Membrane Fusion" (2011). Open Dartmouth: Faculty Open Access Articles. 1535.