The Mechanoenzymatic Core of Dynamin-related Protein 1 Comprises the Minimal Machinery Required for Membrane Constriction

Mitochondria are dynamic organelles that continually undergo cycles of fission and fusion. Dynamin-related protein 1 (Drp1), a large GTPase of the dynamin superfamily, is the main mediator of mitochondrial fission. Like prototypical dynamin, Drp1 is composed of a mechanochemical core consisting of the GTPase, middle, and GTPase effector domain regions. In place of the pleckstrin homology domain in dynamin, however, Drp1 contains an unstructured variable domain, whose function is not yet fully resolved. Here, using time-resolved EM and rigorous statistical analyses, we establish the ability of full-length Drp1 to constrict lipid bilayers through a GTP hydrolysis-dependent mechanism. We also show the variable domain limits premature Drp1 assembly in solution and promotes membrane curvature. Furthermore, the mechanochemical core of Drp1, absent of the variable domain, is sufficient to mediate GTP hydrolysis-dependent membrane constriction. Background: Drp1 oligomerization and activity is critical for mitochondrial fission. Results: GTP hydrolysis is required for Drp1 constriction of lipid bilayers. The variable domain of Drp1 regulates self-assembly and is not required for constriction of lipid bilayers. Conclusion: The core machinery of Drp1 is sufficient to mediate lipid assembly, constriction, and disassembly. Significance: Characterization of the mechanoenzymatic properties of Drp1 advances our understanding of mitochondrial fission.