Summary: Of 21 mutants of 12 five were shown to be mutants by their sensitivity to suppressors. In addition to lacking activity for the overall α-ketoglutarate dehydrogenase complex and the α-ketoglutarate dehydrogenase component (E), the mutants had little or no dihydrolipoyl trans-succinylase (E2) and 20 to 30% less dihydrolipoyl dehydrogenase (E3) than the parental strain. In common with non-suppressible mutants they also had reduced amounts of succinylCoA synthetase and succinate dehydrogenase. Fine structure mapping by P-transduction showed that some of the sites were located in the gene. It is concluded that expression of the region is polarized from to , i.e. synthesis of the E component precedes that of the E2 component. Double mutants with lesions in the pyruvate and α-ketoglutarate dehydrogenase genes () were constructed but their E3 activity was never less than 30% of that of the parental strain. The results are consistent with the existence of separate genes for the dihydrolipoyl dehydrogenase component of the pyruvate and α-ketoglutarate dehydrogenase complexes, but other possibilities could not be ruled out. Further studies on the positions of the four closely-linked tricarboxylic acid cycle genes specifying citrate synthase (), succinate dehydrogenase () and two components of the α-ketoglutarate dehydrogenase complex ( and ) indicate the relative order:


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error