Modelling membrane reshaping by staged polymerization of ESCRT-III filaments.

Modelling membrane reshaping by staged polymerization of ESCRT-III filaments.

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ESCRT-III filaments are composite cytoskeletal polymers that can constrict and cut cell membranes from the inside of the membrane neck.Membrane-bound ESCRT-III filaments undergo a series of dramatic composition and geometry changes in the presence of an ATP-consuming Vps4 enzyme, which causes stepwise changes in the membrane morphology.We set out to understand the physical mechanisms involved in translating the changes in ESCRT-III polymer composition into membrane deformation.We have built a coarse-grained model in which ESCRT-III polymers of different sensationnel kiyari geometries and mechanical properties are allowed to copolymerise and bind to a deformable membrane.

By modelling ATP-driven stepwise depolymerisation of specific polymers, we identify mechanical regimes in which changes in filament composition trigger the associated membrane transition from a flat to a buckled state, and then to a tubule state that eventually undergoes scission to release a small cargo-loaded vesicle.We then characterise how the location and kinetics of polymer loss affects the extent of membrane deformation and the efficiency of membrane neck scission.Our results identify the near-minimal mechanical conditions for the operation of shape-shifting composite polymers merlot redbud tree for sale that sever membrane necks.