Neurospora 6-Phosphogluconate Dehydrogenase

Abstract

Abstract Mutations in two unlinked genes of Neurospora crassa, col-10 and col-3, lead to morphological abnormalities and variant 6-phosphogluconate dehydrogenases (EC 1.1.1.44). The purified mutant enzymes have specific activities, 30 units per mg, similar to the wild type 6-phosphogluconate dehydrogenase, but differ in kinetic parameters, isoelectric points, and thermolability. These properties of the heterocaryon 6-phosphogluconate dehydrogenases are intermediate between those of the wild type and mutant enzymes. Since the morphology of the mutants is restored to nearly that of wild type in the heterocaryons, there is a correlation between the severity of the 6-phosphogluconate dehydrogenase and morphological defects. These results suggest that the col-10 and col-3 genes control the structure of Neurospora 6-phosphogluconate dehydrogenase, and that the altered dehydrogenases are responsible for the mutant morphologies.