Promoter elements and regulation of expression of the cysD gene of Escherichia coli K-12.

The cysD gene, involved in cysteine biosynthesis in Escherichia coli and Salmonella typhimurium, is positively regulated by the CysB regulatory protein. The cysD promoter of E. coli K-12 in a 492-bp PstI-Eco RI fragment was sequenced. The in vivo transcription start point (tsp) for the cysD gene was determined by the methods of T4 DNA polymerase mapping and mung-bean nuclease mapping. The -10 region of the cysD promoter (TATAGT) is closely homologous to the -10 consensus sequence (TATAAT) for E. coli promoters. The -35 region of this promoter (TTCATT) is less closely related to the -35 consensus sequence (TTGACA). Several mutants were obtained by using a chain-termination method for generating unidirectional deletions. Evidence is presented for a possible CysB protein binding site around -89, thought to be involved in regulation of expression of the cysD gene.