Activity of Serratia plymuthica IC1270 gene chiA promoter region in Escherichia coli mutants deficient in global regulators of transcription

To study the regulation of expression of the Serratia plymuthica gene chiA encoding a 58-kDa endochitinase, its 586-bp-long upstream regulatory region was cloned, sequenced and fused to a promoterless lac operon in phage λRS45 to obtain a single-copy transcriptional fusion (P_F1chiA-lac) in lysogens of Escherichia coli wild-type strains or their mutants deficient in various global regulators of transcription. The level of P_F1chiA-lac expression increased about 20- and 90-fold, respectively, in E. coli K12 Δhns and double Δhns stpA mutants deficient in H-NS, and in both H-NS and StpA DNA-binding histone-like proteins, as compared to levels in the wild-type strain. In a Δlrp mutant deficient in the leucine-responsive transcriptional regulator Lrp, the level of P_F1chiA-lac expression increased only up to threefold, whereas even smaller differences relative to the wild-type strain were observed in rpoS and Δcrp mutants deficient in the σ^S subunit of RNA polymerase and catabolite-repression protein (CRP), respectively. Deletion of the inverted-repeat sequences and curved DNA regions located in the upstream region of chiA essentially did not influence strain IC1270's chiA promoter activity in E. coli.