FIG 4.

Negative autoregulation by MraZ. (A) The DNA sequence of the mraZ regulatory region is shown, highlighting P_mra and the O_WT sequence, TGGGN-N₅-TGGGN-N₅-TGGGN. DR1, DR2, and DR3 represent the three DRs separated by the 5-nt spacer regions. (B) β-Galactosidase assays with the WT mraZ-lacZ fusion. WT MG1655 cells carrying a pDSW208 plasmid with no insert (vector) or expressing mraZ, mraW, or both mraZ and mraW were assayed for expression of the mraZ-lacZ reporter on a compatible plasmid (pJE6618). β-Galactosidase activity is expressed in μmol/min/mg protein. Standard deviations were ≤15%. (C) Four different mutant P_mra operator sites are shown. Asterisks indicate the mutagenized DRs. The mutations in the DRs are underlined. (D) Comparison of the β-galactosidase activities of the WT mraZ-lacZ reporter or mutant mraZ-lacZ (O₁ to O₄) reporters regulated by expression from pDSW208 (vector) or (pDSW208/mraZ). Cells were induced with 50 μM IPTG for 30 min. β-Galactosidase activity is expressed in μmol/min/mg protein. One representative experiment is shown.