Fig. 7. Speculative model for the ESCRT-III reaction cycle.
ESCRT-III assembly is initiated when Vps20 binds to Vps25 on the membrane surface. In the second stage, Snf7 binds to the membrane-bound Vps25-Vps20 complex, and this triggers the formation of a membrane-bound Snf7 oligomer. The Snf7 oligomer traps cargo into a localized sorting domain and induces membrane deformation. Vps24 caps the Snf7 oligomer, and interactions between Vps2 and Vps4 initiate membrane disassembly of the ESCRT-III complex (see Discussion).