Auto‐inhibition of dynamin GTPase activity is regulated by PH domain interactions

The dynamin GTPase drives receptor‐mediated endocytosis in addition to other membrane vesicle scission events. We aim to understand how vesicle interactions of the dynamin pleckstrin homology (PH) domain contribute to the conversion of basal, auto‐inhibited dynamin tetramers to an activated, multi‐oligomeric state with a >200‐fold increased rate of GTP hydrolysis. Although dynamin self‐assembly alone has been used to explain this activation, emerging evidence suggests that dynamin may have a more complex conformational interplay between its PH and GTPase domains. Through selective mutagenesis of the dynamin PH domain based on common PH‐GTPase interaction motifs in biology, we have identified an interface of the dynamin PH domain that regulates auto‐inhibition of dynamin GTP hydrolysis rates. Specifically, we find that mutations within this interface fall into two distinct groups: a "weak" class with modestly elevated basal and lipid‐stimulated GTPase activity, as well as an "uncoupled" class whose GTPase rates are elevated ~70‐fold even in the absence of lipid. Funding provided by The Jane Coffin Childs Memorial Fund for Medical Research (JAK) and NIH R01‐GM‐078345 (MAL)