Figure 4. The two stages of dynamin-catalyzed membrane fission.

a. Coarse-grained simulations revealed formation of a stable hemi-fission intermediate (cylinder-like lipid micelle, middle panel) separating the two different stages of membrane fission. Axial cross-sections of representative snapshots from the simulation runs are shown. Localized radial constriction of a membrane tube by a 2 protein-mimetic ring system (effective radius 5-6 nm, inter-ring distance ~10nm) triggered hemi-fission reaction (red arrow). The tilt characterizes the local membrane orientation imposed by the disks²⁶ (see Extended Data Fig. 6A for the ring description). The micelle intermediate remained stable under simulation conditions (see Extended Data Fig. 7) unless a moderate axial force was applied to cause its rupture, thus completing the fission reaction (blue arrow). The rectangular box indicates the dimensions of the cylindrical micelle (~9 × 5.5nm). b. Model of distinct dynamin activities and conformational changes mediating the two-stages of dynamin-catalyzed membrane fission that are required to form the metastable hemi-fission intermediate and then to drive full fission (see Extended Data Fig. 8).