Garrotes, springs. ratchets, and whips: Putting dynamin models to the test

The GTPase dynamin is essential for clathrin-mediated endocytosis, Numerous new and exciting discoveries regarding dynamin function in vivo and in vit ro have led to various models in which dynamin functions directly in membra ne fission and the release of clathrin-coated vesicles from the plasma memb rane. This would make dynamin unique among GTPases in its ability to act as a mechanochemical enzyme. Here we review the various models and their supp orting data. We then discuss new findings that raise doubts as to whether d ynamin breaks the paradigm that governs regulatory GTPases.