The effects of various mutations on MrkH-dependent and -independent transcription of the mrkA promoter.

aβ-galactosidase assays were carried out using E. coli MC4100 derivatives after growth in LB. β-galactosidase activity is the average of three independent experiments, with standard deviation below 15%.bThe pMU2385 derivative contains the WT mrkA regulatory region spanning the positions −190 and +166. All the other mutations described in this Table are based on this plasmid.cShown in parentheses are the values of fold activation, equal to the specific activity of β-galactosidase of the MrkH+ strain divided by that of the MrkH− strain.