FIG. 1.
Identification and initial characterization of 18 ler mutants in autorepression. (A) The pGY1 plasmid, harboring a ler transcriptional fusion to gfp under the control of the native ler promoter (PLEE1), was introduced into a mutS mismatch-repair-deficient strain. The mutated plasmids were recovered and introduced into an EPEC ler::kan strain, and mutants in autorepression were identified as fluorescent colonies. Eighteen mutants were further analyzed. These mutations (B, marked in red) are scattered throughout the Ler amino acid sequence. The predicted coiled-coil and DNA binding motifs are in yellow and light blue, respectively. The core DNA binding domain is underlined. (C) The 18 mutants were reconstructed in pGY1 and the expression of green fluorescent protein, representing the transcription from PLEE1, was measured at late exponential-growth phase. (D) Protein levels of the Ler mutants were analyzed using immunoblot analysis with an anti-Ler antibody.