Interactions of the helix-turn-helix binding domain

Recent studies of members of the helix-turn-helix class of DNA-binding proteins have indicated the importance of non-specific protein-phosphate 'positioning contacts' and revealed several novel features of protein-DNA recognition and binding. These novel features include: the dramatic change in the quaternary structure of Cro (the Cro protein of bacteriophage lambda) on binding specifically to DNA; the striking bending of DNA by the catabolite gene activator protein; the dependence of the DNA-binding specificity of homeodomains on the nature of a single residue of the helix-turn-helix motif; and the specific recognition of minor-groove base pairs by the product of the engrailed gene of Drosophila.