|PROSITE documentation PDOC00041 [for PROSITE entry PS00042]|
The crp-type HTH domain is a DNA-binding, winged helix-turn-helix (wHTH) domain of about 70-75 amino acids present in transcription regulators of the crp-fnr family, involved in the control of virulence factors, enzymes of aromatic ring degradation, nitrogen fixation, photosynthesis, and various types of respiration. The crp-fnr family is named after the first members identified in E.coli: the well characterized cyclic AMP receptor protein CRP or CAP (catabolite activator protein) and the fumarate and nitrate reductase regulator Fnr. crp-type HTH domain proteins occur in most bacteria and in chloroplasts of red algae. The DNA-binding HTH domain is located in the C-terminal part; the N-terminal part of the proteins of the crp-fnr family contains a nucleotide-binding domain (see <PDOC00691>) and a dimerization/linker helix occurs in between. The crp-fnr regulators predominantly act as transcription activators, but can also be important repressors, and respond to diverse intracellular and exogenous signals, such as cAMP, anoxia, redox state, oxidative and nitrosative stress, carbon monoxide, nitric oxide or temperature [1,2].
The structure of the crp-type DNA-binding domain (see <PDB:1LB2>) shows that the helices (H) forming the helix-turn-helix motif (H2-H3) are flanked by two β-hairpin (B) wings, in the topology H1-B1-B2-H2-H3-B3-B4. Helix 3 is termed the recognition helix, as in most wHTHs it binds the DNA major groove [3,4,5].
Some proteins known to contain a Crp-type HTH domain:
The 'helix-turn-helix' DNA-binding motif of these proteins is located in the C-terminal part of the sequence. The pattern we use to detect these proteins starts two residues before the HTH motif and ends two residues before the end of helix 3. We also developed a profile that covers the entire wHTH, including helix 1 and strand 4, and which allows a more sensitive detection.Last update:
April 2006 / Pattern revised.
PROSITE methods (with tools and information) covered by this documentation:
|1||Authors||Irvine A.S. Guest J.R.|
|Title||Lactobacillus casei contains a member of the CRP-FNR family.|
|Source||Nucleic Acids Res. 21:753-753(1993).|
|2||Authors||Koerner H. Sofia H.J. Zumft W.G.|
|Source||FEMS Microbiol. Rev. 27:559-592(2003).|
|3||Authors||Busby S. Ebright R.H.|
|Title||Transcription activation by catabolite activator protein (CAP).|
|Source||J. Mol. Biol. 293:199-213(1999).|
|4||Authors||Lanzilotta W.N. Schuller D.J. Thorsteinsson M.V. Kerby R.L. Roberts G.P. Poulos T.L.|
|Title||Structure of the CO sensing transcription activator CooA.|
|Source||Nat. Struct. Biol. 7:876-880(2000).|
|5||Authors||Huffman J.L. Brennan R.G.|
|Title||Prokaryotic transcription regulators: more than just the helix-turn-helix motif.|
|Source||Curr. Opin. Struct. Biol. 12:98-106(2002).|