The helix-hairpin-helix DNA-binding motif is found to be duplicated in the central domain of RuvA [2]. The HhH domain of DisA, a bacterial checkpoint control protein, is a DNA-binding domain [5].

1: The helix-hairpin-helix DNA-binding motif: a structural basis for non-sequence-specific recognition of DNA. Doherty AJ, Serpell LC, Ponting CP; Nucleic Acids Res 1996;24:2488-2497. PMID:8692686

2: Crystal structure of DNA recombination protein RuvA and a model for its binding to the Holliday junction. Rafferty JB, Sedelnikova SE, Hargreaves D, Artymiuk PJ, Baker PJ, Sharples GJ, Mahdi AA, Lloyd RG, Rice DW; Science 1996;274:415-421. PMID:8832889

3: An evolutionary analysis of the helix-hairpin-helix superfamily of DNA repair glycosylases. Denver DR, Swenson SL, Lynch M; Mol Biol Evol 2003;20:1603-1611. PMID:12832627

4: Common fold in helix-hairpin-helix proteins. Shao X, Grishin NV; Nucleic Acids Res 2000;28:2643-2650. PMID:10908318

5: Structural biochemistry of a bacterial checkpoint protein reveals diadenylate cyclase activity regulated by DNA recombination intermediates. Witte G, Hartung S, Buttner K, Hopfner KP; Mol Cell. 2008;30:167-178. PMID:18439896