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Reconstituted membrane fusion requires regulatory lipids, SNAREs and synergistic SNARE chaperones
Author(s) -
Mima Joji,
Hickey Christopher M,
Xu Hao,
Jun Youngsoo,
Wickner William
Publication year - 2008
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2008.139
Subject(s) - lipid bilayer fusion , biology , microbiology and biotechnology , diacylglycerol kinase , vacuole , snare complex , fusion , phosphatidylserine , liposome , biochemistry , cytoplasm , membrane , phospholipid , signal transduction , linguistics , philosophy , protein kinase c
The homotypic fusion of yeast vacuoles, each with 3Q‐ and 1R‐SNARE, requires SNARE chaperones (Sec17p/Sec18p and HOPS) and regulatory lipids (sterol, diacylglycerol and phosphoinositides). Pairs of liposomes of phosphatidylcholine/phosphatidylserine, bearing three vacuolar Q‐SNAREs on one and the R‐SNARE on the other, undergo slow lipid mixing, but this is unaffected by HOPS and inhibited by Sec17p/Sec18p. To study these essential fusion components, we reconstituted proteoliposomes of a more physiological composition, bearing vacuolar lipids and all four vacuolar SNAREs. Their fusion requires Sec17p/Sec18p and HOPS, and each regulatory lipid is important for rapid fusion. Although SNAREs can cause both fusion and lysis, fusion of these proteoliposomes with Sec17p/Sec18p and HOPS is not accompanied by lysis. Sec17p/Sec18p, which disassemble SNARE complexes, and HOPS, which promotes and proofreads SNARE assembly, act synergistically to form fusion‐competent SNARE complexes, and this synergy requires phosphoinositides. This is the first chemically defined model of the physiological interactions of these conserved fusion catalysts.