A full-length group 1 bacterial sigma factor adopts a compact structure incompatible with DNA binding

Chem Biol. 2008 Oct 20;15(10):1091-103. doi: 10.1016/j.chembiol.2008.09.008.


The sigma 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 sigma 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 sigma1.1. We report the solution structure of Thermotoga maritima sigmaA sigma1.1. We additionally demonstrate by using chemical crosslinking strategies that sigma1.1 is in close proximity to the promoter recognition domains of sigmaA. We therefore propose that sigma1.1 autoinhibits promoter DNA binding of free sigmaA by stabilizing a compact organization of the sigma factor domains that is unable to bind DNA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • DNA / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Binding
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Sigma Factor / chemistry
  • Sigma Factor / genetics
  • Sigma Factor / metabolism*
  • Thermotoga maritima / chemistry
  • Thermotoga maritima / genetics
  • Thermotoga maritima / metabolism*


  • Sigma Factor
  • DNA

Associated data

  • PDB/2K6X