Domain structure and intramolecular regulation of dynamin GTPase

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Abstract
Dynamin is a 100 kDa GTPase required for receptor‐mediated endocytosis, functioning as the key regulator of the late stages of clathrin‐coated vesicle budding. It is specifically targeted to clathrin‐coated pits where it self‐assembles into ‘collars’ required for detachment of coated vesicles from the plasma membrane. Self‐assembly stimulates dynamin GTPase activity. Thus, dynamin–dynamin interactions are critical in regulating its cellular function. We show by crosslinking and analytical ultracentrifugation that dynamin is a tetramer. Using limited proteolysis, we have defined structural domains of dynamin and evaluated the domain interactions and requirements for self‐assembly and GTP binding and hydrolysis. We show that dynamin's C‐terminal proline‐ and arginine‐rich domain (PRD) and dynamin's pleckstrin homology (PH) domain are, respectively, positive and negative regulators of self‐assembly and GTP hydrolysis. Importantly, we have discovered that the α‐helical domain interposed between the PH domain and the PRD interacts with the N‐terminal GTPase domain to stimulate GTP hydrolysis. We term this region the GTPase effector domain (GED) of dynamin.