Dynamin has provided cell biology with one of its most appealing models for protein action. Dynamin has been implicated in the formation of endocytic vesicles, it can self-assemble in vitro into spirals, and (at least with certain acidic lipids) it can act alone to pinch off individual vesicles. A theory therefore arose suggesting that the GTPase activity of dynamin was driving a constriction event by which the spiral pinched off new vesicles.
This model suggests that the hydrolysis of GTP is what drives dynamin action. But, in a 1999 Nature paper, Sever et al., page 1137 of this issue, present an alternative hypothesis. As with other GTPases, it now appears that dynamin is active when it is in its GTP-bound (not GTP-hydrolyzing) form.
The authors use two dynamin mutants that have normal basal GTPase activity, but are defective in...
