PROSITE documentation PDOC00478
Lambdoid phages regulatory protein CIII signature


The lambdoid phage regulatory protein CIII [1] is a very small protein whose presence in the cell results in the stabilization of the CII transcriptional activator, a usually very unstable protein. The stabilized CII protein is then able to activate CI, the gene for the repressor protein which prevents the transcription of proteins necessary for lytic development and thus promotes the establishment of lysogeny.

The exact mechanism of the action of CIII on the stability of CII is not yet known, although it has been proposed that CIII acts as an inhibitor of a protease that degrades CII.

It has been shown that a region of 22 residues, located in the central part of various lambdoid phage CIII's, is the region of highest sequence similarity and sufficient for the activity of the protein. We have derived a pattern from this region.

Last update:

December 1991 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

LAMBDA_PHAGE_CIII, PS00553; Lambdoid phages regulatory protein CIII signature  (PATTERN)


1AuthorsKornitzer D. Altuvia S. Oppenheim A.B.
TitleThe activity of the CIII regulator of lambdoid bacteriophages resides within a 24-amino acid protein domain.
SourceProc. Natl. Acad. Sci. U.S.A. 88:5217-5221(1991).
PubMed ID1828895

PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see prosite_license.html.


View entry in original PROSITE document format
View entry in raw text format (no links)