Figure 1.

(A). Sequence analysis of the upstream region of the pheBA genes in mutant plasmids constitutively expressing the pheBA genes. Data on independent Phe⁺ mutants accumulated in starving cell populations under selective conditions on phenol-minimal plates (postplating mutants) and on the Phe⁺ mutants obtained from independent cultures grown without the selection (preexisting mutants) are summarized. Sequence of the wild-type DNA in pEST1414 (an ≈250-bp DNA region upstream from the pheB gene) is shown. Sequence at the left of the ClaI site is derived from transposon Tn4652 (29). The potential −35 and −10 hexamers of promoters are framed, −35 hexamers by dotted lines, and −10 hexamers by continuous lines. The base substitutions are marked by arrows without any numbering. Deletions are indicated by sloping lines and are numbered; the insertion sites are shown by arrows with underlined italic numbers. (B) Different newly created promoters of the pheBA genes are listed. Two hexamers homologous to the E. coli σ⁷⁰-dependent promoters −35 and −10 consensus sequences are boxed. The promoter sequences for postplating mutants were verified by mapping of the transcription initiation site of the pheBA genes in mutant plasmids as described. Dots mark transcription starting points of the promoters. The different deletion mutants, marked above by numbers at sloping lines, are designated as PDEL2–PDEL45, where the numbers indicate the number of base pairs deleted. The mutants containing base substitutions are designated as PPM. Only one 2-bp insertion mutant, PINS2-AC (marked by 19), is listed. The 70-bp insertion (marked by 20 in A) is of unknown origin.