SUMMARY: Mutants of lt2 requiring acetate or succinate for aerobic growth on glucose were isolated. One acetate-requiring mutant, s8, lacked the activity of the overall pyruvate dehydrogenase complex due to a deficiency in the pyruvate dehydrogenase component (E1p) and was therefore designated an mutant. Another mutant, s6, which required succinate (or lysine plus methionine), lacked activities of the overall α-ketoglutarate dehydrogenase complex and the α-ketoglutarate dehydrogenase component (E1kg) and was designated a mutant. Genetic studies with these mutants established that like k12, lt2 has an gene linked to and thus: , and a gene linked to thus: .

Two deletion strains, sm16 and sm51, which required acetate, or better, acetate plus lysine plus methionine, were found to lack the overall activities of both α-keto acid dehydrogenase complexes. Biochemical and immunological studies showed this to be due to deficiences in pyruvate dehydrogenase and dihydrolipoyl-transacetylase (the E1p and E2p components of the pyruvate complex) and failure to synthesize lipoamide dehydrogenase (the E3 components of both complexes). These deletion strains also behaved as if they lacked the general aromatic permease (), and sm51, which requires nicotinate, was probably deleted for the gene. Genetic studies confirmed that these strains were deleted in the region. The results also indicated that the gene-protein-relationships of the α-keto acid dehydrogenase complexes are similar in and .


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