Binding of the unorthodox transcription activator, Crl, to the components of the transcription machinery Academic Article uri icon


MeSH Major

  • Bacterial Proteins
  • DNA-Directed RNA Polymerases
  • Promoter Regions, Genetic
  • Salmonella enterica
  • Sigma Factor
  • Transcription Factors
  • Transcription, Genetic


  • The small regulatory protein Crl binds to sigmaS, the RNA polymerase stationary phase sigma factor. Crl facilitates the formation of the sigmaS-associated holoenzyme (EsigmaS) and thereby activates sigmaS-dependent genes. Using a real time surface plasmon resonance biosensor, we characterized in greater detail the specificity and mode of action of Crl. Crl specifically forms a 1:1 complex with sigmaS, which results in an increase of the association rate of sigmaS to core RNA polymerase without any effect on the dissociation rate of EsigmaS. Crl is also able to associate with preformed EsigmaS with a higher affinity than with sigmaS alone. Furthermore, even at saturating sigmaS concentrations, Crl significantly increases EsigmaS association with the katN promoter and the productive isomerization of the EsigmaS-katN complex, supporting a direct role of Crl in transcription initiation. Finally, we show that Crl does not bind to sigma70 itself but is able at high concentrations to form a weak and transient 1:1 complex with both core RNA polymerase and the sigma70-associated holoenzyme, leaving open the possibility that Crl might also exert a side regulatory role in the transcriptional activity of additional non-sigmaS holoenzymes.

publication date

  • November 28, 2008



  • Academic Article



  • eng

PubMed Central ID

  • PMC2586269

Digital Object Identifier (DOI)

  • 10.1074/jbc.M807380200

PubMed ID

  • 18818199

Additional Document Info

start page

  • 33455

end page

  • 64


  • 283


  • 48