Characterization of the coated vesicle uncoating ATPase: tissue distribution, association with and activity on intact coated vesicles

We have analyzed the uncoating process of clathrin-coated vesicles (CV) performed by an ATPase (UA; apparent molecular mass 70 kDa) prepared from various mammalian tissues. Our data show that this enzyme removes the clathrin coat from isolated, intact coated vesicles, as seen by sedimentation analysis on gels and also by electron microscopy. The isolated UA does not discriminate between CV from homologous or heterologous tissues. This finding implies that the brain-specific insertion in clathrin light chains cannot be essential for the binding of brain UA to target vesicles. Polyclonal antibodies were raised against UA and were found to inhibit UA activity. Immunoblotting of purified CV and immunoblotting of CV in situ indicate that a subpopulation of CV contains bound UA. However, most of the uncoating enzyme is not associated with coated structures in mammalian tissue culture cells. Our data support the hypothesis that the 70 kDa uncoating ATPase is responsible for the in vivo uncoating of coated vesicles.