Transcription activator CII (IPR007933)

Short name: Transcrpt_activ_CII

Overlapping homologous superfamilies


Family relationships



The CII protein is a transcription activator, conserved in bacteriophage lambda and related phages, that plays a key role in the decision between lytic or lysogenic phage development. CII is regulated at multiple levels including transcription, translation initiation, mRNA stability, and proteolysis [PMID: 12397182]. Conditions that stabilise cII favour lysogenic development.

The lambda CII protein activates three specific promoters, binding to direct repeat sequences rather than the more usual inverted repeats. Structurally, CII is a homotetramer where each monomer is composed of four alpha helices and a disordered C terminus [PMID: 16061804, PMID: 16039594]. The alpha helical region is responsible for DNA binding and multimerisation. The homotetramer has an unusual spatial arrangement that allows recognition of the direct repeat sequences.

GO terms

Biological Process

GO:0006355 regulation of transcription, DNA-templated

Molecular Function

GO:0003677 DNA binding

Cellular Component

No terms assigned in this category.

Contributing signatures

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