The σ factors are the key regulators of bacterial transcription initiation. Through direct read-out of promoter DNA sequence, they recruit the core RNA polymerase to sites of initiation, thereby dictating the RNA polymerase promoter-specificity. The group 1 σ factors, which direct the vast majority of transcription initiation during log phase growth and are essential for viability, are autoregulated by an N-terminal sequence known as σ1.1. We report the solution structure of Thermotoga maritima σA σ1.1. We additionally demonstrate by using chemical crosslinking strategies that σ1.1 is in close proximity to the promoter recognition domains of σA. We therefore propose that σ1.1 autoinhibits promoter DNA binding of free σA by stabilizing a compact organization of the σ factor domains that is unable to bind DNA.
All Science Journal Classification (ASJC) codes
- Molecular Medicine
- Molecular Biology
- Drug Discovery
- Clinical Biochemistry