THE OGD1-MUTANT AND KGD1-MUTANT LACKING 2-OXOGLUTARATE DEHYDROGENASE-ACTIVITY IN YEAST ARE ALLELIC AND CAN BE DIFFERENTIATED BY THE CLONED AMBER SUPPRESSOR

The activity of mitochondrial 2-oxoglutarate dehydrogenase in S. cerev isiae can be impaired either by the ogd1 or the kgd1 mutation. The OGD 1 gene and two suppressor genes were isolated by complementation of th e ogd1 mutant. The complementation of the kdg1 mutant by the OGD1 gene , an allelism test, and meiotic mapping, revealed that the ogd1 and kg d1 mutations are allelic. The two mutations were differentiated by the cloned suppressor gene which was able to partially complement ogd1, b ut not kgd1. The molecular analysis of the suppressor gene revealed it s identity with the natural tRNA(CAG)Gln gene found in the upstream re gion of URA10.