RNAP-Promoter interactions: promoter
recognition and binding by σ (sigma) factor
Core enzyme requires the addition of the σ
factor (forming holoenzyme) to be able to recognize the promoter
elements. The six base pairs on the -10 region, two on the extended -10
region, and six base pairs on the -35 region of is recognized by domains
2, 3, and 4 of σ factor, respectively.
Promoter sequence can vary in "strength"
depending on its deviation from its consensus sequence. Similarly,
each σ factor has an affinity for different promoter sequences.
These interactions contribute to gene regulation in prokaryotes by
putting various genes under control of separate σ factors. RNAP-promoter
interactions are, therefore, key to the control of gene expression.
Interaction with the -10 and extended -10 (x-10)
The five σ residues important for binding
to -10 element and the two residues important for the binding of the
x-10 element are highlighted.
Interaction with the -35 promoter elements
The four σ
residues important for binding to -35 element are shown.
Highlight of all residues interacting with
elements on DNA are highlighted in blue.
JMol script and text by