Sigma factor
Sigma (σ) factor is a small protein subunit, which associates with the core RNA polymerase, to form a holoenzyme. It recognises a specific sequence of DNA, the promotor, where the holoenzyme binds tightly to the DNA, initiating transcription. The sigma factor increases the affinity of RNA polymerase for the promotor region. After transcription has progressed about 10 bases the sigma factor is released[1]. In E. coli the main sigma factor is σ 70, however, many others exist.
References
- ↑ Alberts, Johnson, Lewis, Raff, Roberts, Walter (2008) Molecular Biology of the Cell, 5th Edition. New York: Garland Science p336