The ATPase activity of purified CDC48p from Saccharomyces cerevisiae shows complex dependence on ATP-, ADP-, and NADH-concentrations and is completely inhibited by NEM.

The cell cycle protein CDC48p from Saccharomyces cerevisiae is a member of a protein superfamily (AAA superfamily) characterized by a common region of approximately 200 amino-acid residues including an ATP binding consensus. CDC48p purified to homogeneity showed considerable ATPase activity which could be completely abolished by preincubation with NEM in the absence of ATP. ATP protects the protein from NEM and stabilizes the otherwise labile enzyme. The ATPase activity is reversibly inhibited by NADH and shows cooperativity with its substrate ATP. The application of the in vitro ATPase activity to the identification of physiologically interacting molecules is discussed. By electron microscopy, the enzyme was shown to consist of hexameric ring structures similar to its vertebrate homologue.