RNA directed synthesis of catalytically active Drosophila sn-glycerol-3-phosphate dehydrogenase in Xenopus oocytes.

Xenopus laevis oocytes injected with poly(A)+ RNA isolated from Drosophila melanogaster direct the synthesis of catalytically active glycerol-3-phosphate dehydrogenase (NAD+) (EC 1.1.1.8). The de novo synthesized enzyme reflects the electrophoretic properties appropriate to the stock of flies from which the injected RNA was isolated and is electrophoretically distinct from endogenous Xenopus activity. Immunoprecipitation of 35S-labeled translation products has demonstrated two immunologically related proteins with molecular masses of 32- and 34kDa which are encoded by two separate mRNA molecules. The 32-kDa protein is identical in size and charge properties to the protein purified from the fly and possesses the catalytic activity observed in the Xenopus translational assay. Poly(A)+ RNA isolated from a strain of flies bearing a CRM- null mutation at the GPDH locus does not contain translatable RNA for the 32-kDa protein. These results suggest that the two immunologically related proteins are the translational products of two separate transcripts derived from either two related loci or from differential transcription and/or processing of the same genetic locus.