Cloning and Expression of the Succinyl-CoA Synthetase Genes of Escherichia coli K12

Abstract

Summary: The genes encoding both subunits of the succinyl-CoA synthetase of Escherichia coli have been identified as distal genes of the suc operon, which also encodes the dehydrogenase (Elo; sucA) and succinyltransferase (E20; sucB) components of the 2-oxoglutarate dehydrogenase complex. The newly defined genes express polypeptides of 41 kDa (sucC) and 31 kDa (sucD), corresponding to the β and α subunits of succinyl-CoA synthetase, respectively. The genes are thus located at 16·8 min in the E. coli linkage map, together with the citrate synthase (gltA) and succinate dehydrogenase (sdh) genes, in a cluster of nine citric acid cycle genes: gltA-sdhCDABE-sucABCb. Four deletion strains lacking all of these citric acid cycle enzymes were characterized. The succinyl-CoA synthetase activities of strains harbouring plasmids containing the sucC and sucD genes were amplified some fourfold. Further emzymological studies indicated that expression of succinyl-CoA synthetase is coordinately regulated with 2-oxoglutarate dehydrogenase.