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Geometric Catalysis of Membrane Fission Driven by Flexible Dynamin Rings

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Science  22 Mar 2013:
Vol. 339, Issue 6126, pp. 1433-1436
DOI: 10.1126/science.1233920

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Making the Cut

Dynamin is the prototypical member of a large family of structurally related guanosine triphosphatases involved in membrane fission and fusion. A variety of models have been suggested to explain how dynamin works. Shnyrova et al. (p. 1433; see the Perspective by Holz) reconstituted dynamin-mediated membrane scission on lipid nanotubes and suggest a molecular model for dynamin activity that takes into consideration all known aspects of dynamin function.

Abstract

Biological membrane fission requires protein-driven stress. The guanosine triphosphatase (GTPase) dynamin builds up membrane stress by polymerizing into a helical collar that constricts the neck of budding vesicles. How this curvature stress mediates nonleaky membrane remodeling is actively debated. Using lipid nanotubes as substrates to directly measure geometric intermediates of the fission pathway, we found that GTP hydrolysis limits dynamin polymerization into short, metastable collars that are optimal for fission. Collars as short as two rungs translated radial constriction to reversible hemifission via membrane wedging of the pleckstrin homology domains (PHDs) of dynamin. Modeling revealed that tilting of the PHDs to conform with membrane deformations creates the low-energy pathway for hemifission. This local coordination of dynamin and lipids suggests how membranes can be remodeled in cells.

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