use of sigma 54 as transcription factor
What is a sigma factor?
- prokaryotic transcription initiation factor
- enables binding of RNA polymerase to gene promoter
- activation dependent on different environmental conditions
sigma 54 versus sigma70
- There is limited amino-acid similarity between sigma54 and sigma70.
- sigma70-RNAP: positive and negative regulation
- transcribes most housekeeping genes
- RNAP–70 holoenzyme is competent for transcription
- sigma54-RNAP: positive regulation
- controls transcription of genes expressed under specific environmental conditions
- RNAP–54 complex binds to promoter DNA, but remains stalled and unable to transcribe. When the activator protein PspF binds to a bacterial enhancer-like sequence in the promoter and hydrolyses ATP, the RNAP–54 complex is converted from a closed to an open complex that can actively transcribe. Activation of RNAP–54 transcription by PspF (activator protein) is analogous to activation of RNA polymerase II-mediated transcription in eukaryotes by the ATP-hydrolysing protein TFIIH.[]
- less basal transcription which means less noise.[]