Domain

RNA polymerase sigma-70 region 4 (IPR007630)

Short name: RNA_pol_sigma70_r4

Domain relationships

None.

Description

The bacterial core RNA polymerase complex, which consists of five subunits, is sufficient for transcription elongation and termination but is unable to initiate transcription. Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme [PMID: 3052291]. RNA polymerase recruits alternative sigma factors as a means of switching on specific regulons. Most bacteria express a multiplicity of sigma factors. Two of these factors, sigma-70 (gene rpoD), generally known as the major or primary sigma factor, and sigma-54 (gene rpoN or ntrA) direct the transcription of a wide variety of genes. The other sigma factors, known as alternative sigma factors, are required for the transcription of specific subsets of genes.

With regard to sequence similarity, sigma factors can be grouped into two classes, the sigma-54 and sigma-70 families. Sequence alignments of the sigma70 family members reveal four conserved regions that can be further divided into subregions eg. sub-region 2.2, which may be involved in the binding of the sigma factor to the core RNA polymerase; and sub-region 4.2, which seems to harbor a DNA-binding 'helix-turn-helix' motif involved in binding the conserved -35 region of promoters recognised by the major sigma factors [PMID: 3092189, PMID: 1597408].

Region 4 of sigma-70 like sigma-factors is involved in binding to the -35 promoter element via a helix-turn-helix motif [PMID: 11931761]. Due to the way Pfam works, the threshold has been set artificially high to prevent overlaps with other helix-turn-helix families. Therefore there are many false negatives.

GO terms

Biological Process

GO:0006352 DNA-templated transcription, initiation
GO:0006355 regulation of transcription, DNA-templated

Molecular Function

GO:0003677 DNA binding
GO:0003700 sequence-specific DNA binding transcription factor activity
GO:0016987 sigma factor activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam