FIG. 1.

Sequences of σ³² and the groE promoter. (A) CLUSTAL alignment of E. coli sigma factors σ³² and σ⁷⁰. Sequences are presented in the one-letter code; identical residues are shown in bold. Numbers on the left of each lane indicate amino acid positions relative to the start of each protein sequence. Region 2.3 is thought to be involved in promoter DNA melting, region 2.4 in the recognition of the −10 promoter element, and region 4.2 in the recognition of the −35 promoter element. (B) The groE promoter recognized by holoenzyme containing σ³², used here to drive transcription of the β-galactosidase reporter gene. The −10 and −35 regions are indicated in bold lettering.