The characterization of alpha-glycerophosphate dehydrogenase mutants in Drosophila melanogaster

Thirty mutants of alpha-glycerophosphate dehydrogenase (alpha GPDH, EC 1.1.1.8) from Drosophila melanogaster were produced with the chemical mutagen ethyl methanesulfonate (EMS). These mutants and nine others previously obtained have been characterized with respect to level of enzymatic activity, viability, flight ability, and presence of cross-reacting material (CRM). The presence of alpha GPDH mRNA in several of the mutans has been tested by in vitro translation. There are strong correlations between the level of enzyme activity, viability and flight ability. Thirteen of the mutants are CRM- by solution immunoprecipitation experiments, but of these, only three are CRM- by a more sensitive 125I-protein A-based radioimmune gel assay. The viability of the three CRM- mutants suggests that the absence of alpha GPDH protein is not a lethal condition. The immunoprecipitated protein of the low activity mutant, alpha GpdhnGL3, has a smaller apparent molecular weight on polyacrylamide-SDS gels than does the protein from wild type. Criteria for the identification of nonsense mutations in Drosophila are discussed.