Taxonomic distribution of proteins containing HTH_XRE domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing HTH_XRE domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Characterisation of a repressor gene (xre) and a temperature-sensitive allele from the Bacillus subtilis prophage, PBSX.

Wood HE, Devine KM, McConnell DJ
Gene. 1990; 96: 83-8

The defective prophage of Bacillus subtilis 168, PBSX, is a chromosomally based element which encodes a non-infectious phage-like particle with bactericidal activity. PBSX is induced by agents which elicit the SOS response. In a PBSX thermoinducible strain which carries the xhi1479 mutation, PBSX is induced by raising the growth temperature from 37 degrees C to 48 degrees C. A 1.2-kb fragment has been cloned which complements the xhi1479 mutation. The nucleotide sequence of this fragment contains an open reading frame (ORF) which encodes a protein of 113 amino acids (aa). This aa sequence resembles that of other bacteriophage repressors and suggests that the N-terminal region forms a helix-turn-helix motif, typical of the DNA-binding domain of many bacterial regulatory proteins. The ORF is preceded by four 15-bp direct repeats, each of which contains an internal palindromic sequence, and by sequences resembling a SigA-dependent promoter. The nt sequence of an equivalent fragment from the PBSX thermoinducible strain has also been determined. There are three aa differences within the ORF compared to the wild type, one of which lies within the helix-turn-helix segment. This ORF encodes a repressor protein of PBSX.

Structure of the amino-terminal domain of phage 434 repressor at 2.0 A resolution.

Mondragon A, Subbiah S, Almo SC, Drottar M, Harrison SC
J Mol Biol. 1989; 205: 189-200

The crystal structure of the amino-terminal domain of phage 434 repressor has been solved using molecular replacement methods and refined to an R-factor of 19.3% against data to 2.0 A resolution. The protein comprises five short alpha-helices. Two of these form a helix-turn-helix motif, very similar to those found in related proteins. The protein is remarkably similar to the Cro protein from the same phage.