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  • HOPS recognizes each SNARE, assembling ternary trans-complexes for rapid fusion upon engagement with the 4th SNARE.

HOPS recognizes each SNARE, assembling ternary trans-complexes for rapid fusion upon engagement with the 4th SNARE.

eLife (2020-01-22)
Hongki Song, Amy S Orr, Miriam Lee, Max E Harner, William T Wickner
ABSTRACT

Yeast vacuole fusion requires R-SNARE, Q-SNAREs, and HOPS. A HOPS SM-family subunit binds the R- and Qa-SNAREs. We now report that HOPS binds each of the four SNAREs. HOPS catalyzes fusion when the Q-SNAREs are not pre-assembled, ushering them into a functional complex. Co-incubation of HOPS, proteoliposomes bearing R-SNARE, and proteoliposomes with any two Q-SNAREs yields a rapid-fusion complex with 3 SNAREs in a trans-assembly. The missing Q-SNARE then induces sudden fusion. HOPS can 'template' SNARE complex assembly through SM recognition of R- and Qa-SNAREs. Though the Qa-SNARE is essential for spontaneous SNARE assembly, HOPS also assembles a rapid-fusion complex between R- and QbQc-SNARE proteoliposomes in the absence of Qa-SNARE, awaiting Qa for fusion. HOPS-dependent fusion is saturable at low concentrations of each Q-SNARE, showing binding site functionality. HOPS thus tethers membranes and recognizes each SNARE, assembling R+Qa or R+QbQc rapid fusion intermediates.

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Sigma-Aldrich
1,2-Dipalmitoyl-sn-glycerol, ≥99%