Molecular tools for inactivating a yeast enzyme in vivo

As part of an effort to develop a new means of inducibly inactivating cellular proteins in vivo, three monoclonal antibodies which neutralize yeast alcohol dehydrogenase (ADH) activity were isolated and characterized with respect to criteria important for the inactivation strategy. The significance of these criteria is considered, and a general means of generating appropriate antibodies is suggested. All three antibodies described here were specific for ADH I; they did not recognize the closely related isozyme ADH II in a plate-binding assay and did not immunoprecipitate molecules other than ADH from a Saccharomyces cerevisiae extract. Neutralization occurred in a yeast extract and, for two antibodies, was blocked by high concentrations of the coenzyme NAD+. This finding suggests that the antibodies may block enzyme activity by stabilizing an inactive form of ADH lacking bound NAD+. These results provide a foundation for the use of these antibodies to inactivate ADH in vivo.