FIG. 3.

Structures of Rob and MarA proteins bound to micF and marRAB marboxes, respectively. The highly homologous DNA-binding domains of Rob and MarA are colored orange, with their respective HTH recognition helices in brown and the additional C-terminal putative ligand-binding domain of Rob in blue. The N-terminal Rob HTH is inserted into the major groove, whereas the C-terminal HTH makes contacts only to the DNA backbone. In contrast, MarA induces a significant bend in the marRAB promoter to facilitate the placement of both HTH motifs in successive major grooves of marRAB marbox DNA. (Reprinted with permission from reference 89; kindly provided by Tom Ellenberger.)