Categorization of biochemically characterized Mga-regulated promoters. Mga-regulated promoters fall into three categories on the basis of the number and location of Mga-binding sites (gray boxes) in relation to the transcriptional start sites (arrows). In category A, a single Mga-binding site exists proximal to the start of transcription. In category B, a single Mga-binding site exists distal to the start of transcription, while a second low-affinity Mga-binding site proximal to the start of transcription (dashed box) may be present. The single category C promoter, Pmga, has multiple binding sites that are larger than those in the other two categories (59 bp versus 45 bp) and are located between two transcriptional start sites. Position numbers are given in relation to the transcriptional start site, which is numbered +1. Dark gray boxes represent the translational coding region for each gene.