Membranes linked by trans-SNARE complexes require lipids prone to non-bilayer structure for progression to fusion
Michael Zick,
Christopher Stroupe,
Amy Orr,
Deborah Douville,
William T Wickner
Affiliations
Michael Zick
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
Christopher Stroupe
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States; Center for Membrane Biology, University of Virginia, Charlottesville, United States
Amy Orr
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
Deborah Douville
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
William T Wickner
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
Like other intracellular fusion events, the homotypic fusion of yeast vacuoles requires a Rab GTPase, a large Rab effector complex, SNARE proteins which can form a 4-helical bundle, and the SNARE disassembly chaperones Sec17p and Sec18p. In addition to these proteins, specific vacuole lipids are required for efficient fusion in vivo and with the purified organelle. Reconstitution of vacuole fusion with all purified components reveals that high SNARE levels can mask the requirement for a complex mixture of vacuole lipids. At lower, more physiological SNARE levels, neutral lipids with small headgroups that tend to form non-bilayer structures (phosphatidylethanolamine, diacylglycerol, and ergosterol) are essential. Membranes without these three lipids can dock and complete trans-SNARE pairing but cannot rearrange their lipids for fusion.
