Purification of active HOPS complex reveals its affinities for phosphoinositides and the SNARE Vam7p.
Coupling of Rab GTPase activation and SNARE complex assembly during membrane fusion is poorly understood. The homotypic fusion and vacuole protein sorting (HOPS) complex links these two processes: it is an effector for the vacuolar Rab GTPase Ypt7p and is required for vacuolar SNARE complex assembly. We now report that pure, active HOPS complex binds phosphoinositides and the PX domain of the vacuolar SNARE protein Vam7p. These binding interactions support HOPS complex association with the vacuole and explain its enrichment at the same microdomains on docked vacuoles as phosphoinositides, Ypt7p, Vam7p, and the other SNARE proteins. Concentration of the HOPS complex at these microdomains may be a key factor for coupling Rab GTPase activation to SNARE complex assembly.
Stroupe
Christopher
C
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA.
Collins
Kevin M
KM
Fratti
Rutilio A
RA
Wickner
William
W
D008561:Membrane Fusion; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D050767:Qc-SNARE Proteins / Q000302:isolation & purification / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000302:isolation & purification / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D014617:Vacuoles / Q000502:physiology*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
D010716:Phosphatidylinositols; D050767:Qc-SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; C494205:VAM7 protein, S cerevisiae; C079005:YPT7 protein, S cerevisiae; D020691:rab GTP-Binding Proteins