Dynamin GTPase, a force-generating molecular switch.

Dynamin is a GTPase that regulates late events in clathrin-coated vesicle formation. Our current working model suggests that dynamin is targeted to coated pits in its unoccupied or GDP-bound form, where it is initially distributed uniformly throughout the clathrin lattice. GTP/GDP exchange triggers its release from these sites and its assembly into short helices that encircle the necks of invaginated coated pits like a collar. GTP hydrolysis, which is required for vesicle detachment, presumably induces a concerted conformation change, tightening the collar. Unlike most of its GTPase cousins that serve as molecular switches, dynamin has a low affinity for GTP, a very high intrinsic rate of GTP hydrolysis and functions as a homo-oligomer. A concerted conformational change resulting from coordinated GTP hydrolysis by the dynamin oligomer might be sufficient to generate force. In this case, dynamin would be the first GTPase identified that acts as a structural protein with mechano-chemical function.