The alpha glycerophosphate cycle in Drosophila melanogaster V. molecular analysis of alpha glycerophosphate dehydrogenase and alpha glycerophosphate oxidase mutants

Abstract

Two enzymes, alpha glycerophosphate dehydrogenase (GPDH-1) in the cytoplasm and alpha glycerophosphate oxidase (GPO-1) in the mitochondrion cooperate in Drosophila flight muscles to generate the ATP needed for muscle contraction. Null mutants for either enzyme cannot fly. Here, we characterize 15 ethyl methane sulfonate (EMS)-induced mutants in GPDH-1 at the molecular level and assess their effects on structural and evolutionarily conserved domains of this enzyme. In addition, we molecularly characterize 3 EMS-induced GPO-1 mutants and excisions of a P element insertion in the GPO-1 gene. The latter represent the best candidate for null or amorphic mutants in this gene.

Figure 1

Positions of the GPDH-1 mutations in the wild-type protein sequence. NAD-binding and catalytic domains are boxed as shown. Mutant sites are indicated in red and the mutant amino acids listed in Table 2. The position of the splice site variant, nsp4, is indicated by a triangle. (This figure appears in color in the online version of Journal of Heredity.)

Figure 2

Positions of the EMS-induced mutants (down arrow), insertions (triangle), and imprecise excisions (bar) in the GPO-1 gene. Constitutive exons are shown as open boxes and 5′UTR regions with alternative transcriptional start sites as arrowed boxes.