Video 3. Model of Vps4 assembly and ESCRT-III disassembly.
Vps4 (purple) is recruited to the ESCRT-III lattice (green) through binding of its N-terminal MIT domain to MIT Interacting Motifs (MIMs) (Kieffer et al., 2008; Obita et al., 2007; Stuchell-Brereton et al., 2007), which are sequences at the ends of the long, flexible C-terminal tails of ESCRT-III subunits. The avidity effect of the ESCRT-III polymer promotes Vps4 hexamerization around flexible ESCRT-III sequences. The hexamer is further stabilized by the dimeric Vta1 protein (tan), which also concentrates at the ESCRT-III polymer through its N-terminal t-MIT domain (not shown) (Guo and Xu, 2015; Skalicky et al., 2012; Vild et al., 2015). The Vps4 hexamer hydrolyzes ATP and translocates the substrate through the central pore, thereby destabilizing the ESCRT-III structure and removing the subunit from the lattice. We speculate that Vps4 and Vta1 remain bound to the ESCRT-III lattice via their MIT domains such that they are in position to process additional ESCRT-III subunits until the polymer is disassembled. This animation was created using Autodesk Maya (Autodesk, Inc.) from protein structural models exported from UCSF Chimera (Pettersen et al., 2004).