Cysteine regulon

Figure 12.17 Important targets for the generation of an L-cysteine production strain. Mutant proteins are marked with an asterisk. Exp. cysteine export proteins. SerA 3-phosphoglycerate dehydrogenase. CysE serine transacetylase. CysB transcriptional activator of the cystein regulon. CysK O-acetyl-L-serine (thiol)-lyase A. CysM O-acetyl-L-serine (thiol)-lyase B.

The proteins NodP (ATP sulfurylase) and NodQ (adenosine 5 -phosphosulfate (APS) kinase) are associated in a sulfate-activating complex that enables the synthesis of the sulfate donor (PAPS) for Nod factor sulfation [42]. PAPS is also the sulfate donor used for the synthesis of cysteine and it is produced in E. coli by the normal household proteins CysC, CysD, and CysN [43, 44]. The genes cysCDN are part of the cysteine regulon which is repressed in the presence of cysteine and other reduced sulfur compounds [45]. This means that the E. coli machinery of PAPS biosynthesis can be used for chitin oligosaccharide sulfation if the bacteria are cultivated with sulfate as the only sulfur source. The total PAPS demand for the synthesis of cysteine and methionine (87 and 146 pmol g dried cells, respectively) [46] largely exceeds the maximum demand that can be estimated for chitin oligosaccharide sulfation (around 20 pmol g dried cells). 

Grundy FJ, Henkin TM. The S box regulon a new global transcription termination control system for methionine and cysteine biosynthesis genes in gram-positive bacteria. Mol. Microbiol. 1998 30 737-749. 

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