Dynamin is recruited to the growing vesicle and, under conditions that interfere with its GTPase activity, dynamin forms a collar or ring around the neck of the budding vesicle. It is unclear whether dynamin acts as a mechanochemical transducer to generate fission or as a recruiter to attach other proteins that are directly responsible for the fission step. Lipid-modifying enzymes such as endophilin are also involved in vesicle formation. Endophilin is an acyltransferase that interacts with dynamin and that generates lysophosphatidic acid. The current view is that this reaction produces a negative curvature at the neck of the vesicle.