The name of this superfamily has been modified since the most recent official CATH+ release (v4_3_0). At the point of the last release, this superfamily was: waiting to be named.

Functional Families

Overview of the Structural Clusters (SC) and Functional Families within this CATH Superfamily. Clusters with a representative structure are represented by a filled circle.

Superfamily: RNA polymerase sigma factor, region 2, helix turn helix motif

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. 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, Sigma70 (gene rpoD; major sigma factor) and Sigma54 (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.

This superfamily entry consists of a structural domain containing a helix turn helix motif. It is located in region 2 (sigma2 domain) found in several sigma factors, often in conjunction with sigma3 and sigma4 domains (INTERPRO:IPR013324). This region is present in Sigma70, Sigma28 (FliA), SigA, SigR and RpoE and it is a often a variable insert subdomain.


GO Diversity

Unique GO annotations
70 Unique GO terms

EC Diversity

Unique EC annotations
2 Unique EC terms

Species Diversity

Unique species annotations
19281 Unique species

Sequence/Structure Diversity

Overview of the sequence / structure diversity of this superfamily compared to other superfamilies in CATH. Click on the chart to view the data in more detail.

Superfamily Summary

A general summary of information for this superfamily.
Domains: 197
Domain clusters (>95% seq id): 23
Domain clusters (>35% seq id): 16
Unique PDBs: 111
Structural Clusters (5A): 2
Structural Clusters (9A): 2
FunFam Clusters: 51
Unique EC: 2
Unique GO: 70
Unique Species: 19281