Extended Data Figure 8. Dynamin-catalyzed membrane fission occurs in two mechanistically distinct stages through a hemi-fission intermediate.

Model overlaying the distinct dynamin activities and conformational changes onto the two energy barriers (green curve) that must be overcome, first to catalyze formation of the metastable hemi-fission intermediate and subsequently to drive full fission. When trapped in the transition-state and in the absence of GTP, CxC-Dyn1 can drive the formation of a metastable and flickering hemi-fission state (solid blue curve) through the assembly of small scaffolds and enhanced wedging activity of the PHD. However, without subsequent GTPase driven conformational changes required to loosen the scaffold, generate axial force and retract the PHD, as occurs for WT-Dyn1 (dotted blue line), the membrane-bound CxC-Dyn1 creates an insurmountable barrier to fission (dashed blue line).