Molecular genetic aspects of the citric acid cycle of Escherichia coli.

The genes encoding all of the citric acid cycle enzymes of Escherichia coli have been cloned and much has been learned about the structure, function and expression of these enzymes from the nucleotide sequences, the mRNA transcripts and site-directed mutagenesis of the corresponding genes. Special features of the expression of the aerobic cycle, and its anaerobic transformation into a branched pathway in a facultative anaerobe, are considered. Aspects of the structure-function relationships of succinate dehydrogenase, succinyl-CoA synthetase, fumarase and related enzymes, and the 2-oxo acid dehydrogenase complexes are reviewed.