GTPase activity of dynamin and resulting conformation change are essentialfor endocytosis

Dynamin is a large GTPase with a relative molecular mass of 96,000 (M-r 96K ) that is involved in clathrin-mediated endocytosis and other vesicular tra fficking processes(1,2). Although its function is apparently essential for scission of newly formed vesicles from the plasma membrane, the nature of d ynamin's role in the scission process is still unclear(3,4). It has been pr oposed that dynamin is a regulator (similar to classical G proteins) of dow nstream effectors(5). Here we report the analysis of several point mutants of dynamin's GTPase effector (GED) and GTPase domains. We show that oligome rization and GTP binding alone, by dynamin, are not sufficient for endocyto sis in vivo. Rather, efficient GTP hydrolysis and an associated conformatio nal change are also required. These data argue that dynamin has a mechanoch emical function in vesicle scission.