The Escherichia coli starvation gene cstC is involved in amino acid catabolism

Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. They are also compromised in starvation survival, where amino acid catabolism is important. The cstC gene encodes a 406-amino-acid protein that closely resembles the E. coli ArgD protein, which is involved in arginine biosynthesis. We postulate that CstC is a counterpart of ArgD in an amino acid catabolic pathway. The cstC upstream region contains several regulatory consensus sequences. Both sigma(S) and sigma(54) promoters are probably involved in cstC transcription and appear to compete with each other, presumably to match cstC expression to the cellular amino acid catabolic needs.