|PROSITE documentation PDOC50943|
The cro/C1-type HTH domain is a DNA-binding, helix-turn-helix (HTH) domain of about 50-60 residues present in transcriptional regulators. The domain is named after the transcriptional repressors cro and C1 of temperate bacteriophages 434 and lambda, respectively. Besides in bacteriophages, cro/C1-type regulators are present in prokaryotes and in eukaryotes. The helix-turn-helix DNA-binding motif is generally located in the N-terminal part of these transcriptional regulators. The C-terminal part may contain an oligomerization domain, e.g. C1 repressors and CopR act as dimers, while SinR is a tetramer. The cro/C1-type HTH domain also occurs in combination with the TPR repeat and the C-terminal part of C-5 cytosine-specific DNA methylases contains regions related to the enzymatic function (see <PDOC00089>).
Several structures of cro/C1-type transcriptional repressors have been resolved and their DNA-binding domain encompasses five α helices, of which the extremities are less conserved (see <PDB:2OR1>) . The helix-turn-helix motif comprises the second and third helices, the third being called the recognition helix. The HTH is involved in DNA-binding into the major groove, where the recognition helix makes most DNA-contacts. The bacteriophage repressors regulate lysogeny/lytic growth by binding with differential affinity to the operators. These operators show 2-fold symmetry and the repressors bind as dimers. Binding of the repressor to the operator positions the DNA backbone into a slightly bent twist [1,2].
Some proteins known to contain a cro/C1-type HTH domain:
The profile we developed covers the entire DNA-binding domain, from the major part of helix 1, including the helix-turn-helix motif and the major part of helix 5.Last update:
November 2003 / First entry.
PROSITE method (with tools and information) covered by this documentation:
|1||Authors||Aggarwal A.K., Rodgers D.W., Drottar M., Ptashne M., Harrison S.C.|
|Title||Recognition of a DNA operator by the repressor of phage 434: a view at high resolution.|
|2||Authors||Steinmetzer K., Behlke J., Brantl S., Lorenz M.|
|Title||CopR binds and bends its target DNA: a footprinting and fluorescence resonance energy transfer study.|
|Source||Nucleic Acids Res. 30:2052-2060(2002).|
|3||Authors||Lewis R.J., Brannigan J.A., Offen W.A., Smith I., Wilkinson A.J.|
|Title||An evolutionary link between sporulation and prophage induction in the structure of a repressor:anti-repressor complex.|
|Source||J. Mol. Biol. 283:907-912(1998).|
|4||Authors||Takemaru K., Li F.Q., Ueda H., Hirose S.|
|Title||Multiprotein bridging factor 1 (MBF1) is an evolutionarily conserved transcriptional coactivator that connects a regulatory factor and TATA element-binding protein.|
|Source||Proc. Natl. Acad. Sci. U.S.A. 94:7251-7256(1997).|
|5||Authors||Kabe Y., Goto M., Shima D., Imai T., Wada T., Morohashi K., Shirakawa M., Hirose S., Handa H.|
|Title||The role of human MBF1 as a transcriptional coactivator.|
|Source||J. Biol. Chem. 274:34196-34202(1999).|