Promoters/Overview

The registry symbol for a promoter is shown above a typical sequence for a bacterial promoter. The lavender shaded boxes indicate the two most conserved regions of a bacterial promoter and are located at -10 and -35 bases from the transcriptional start site (shaded in green). There are, on average, 17bp between the -10 and -35 sites and 7bp between the -10 site and the transcriptional start site pribnowharleylisser1lisser2.

A promoter is a DNA sequence that can recruit transcriptional machinery and lead to transcription of the downstream DNA sequence. The specific sequence of the promoter determines the strength of the promoter (where a strong promoter is one that leads to a high rate of transcription initiation ).

In addition to sequences that "promote" transcription, a promoter may include additional sequences known as operators that control the strength of the promoter. For example, a promoter may include a binding site for a protein that attracts or obstructs the RNAP binding to the promoter. The presence or absence of the protein will affect the strength of the promoter. Such a promoter is known as a regulated promoter.