Structures of Rex alone and in complex with Rex ROP DNA.

Cartoon representations of Rex in complex with NAD+ (A and B) and NAD+ and DNA (C). The nucleotide binding domain (NBD) that binds NAD+ and NADH and the winged helix domain (WHD) that interacts with DNA are indicated. D. Superposition of the three structures. The wing of the WHD is coloured blue and the recognition helix (α-helix 3) that makes sequence-specific DNA contacts is coloured red. E. Schematic representation of protein–DNA interactions in the Rex-ROP complex. Due to the symmetric nature of the complex only half of the 22 bp DNA is shown. Hydrogen bonds are shown as dotted lines and van der Waals contacts as solid lines. Residues that make contacts with the phosphate moieties are indicated. F. Overall structure of the Rex-DNA complex with one Rex subunit coloured grey and the other green. Close up of the Rex-DNA interactions (corresponding to the boxed region). For clarity only the wing and the recognition helix of Rex is shown. Residues that form hydrogen bonds (dotted green lines) to the bases of DNA are labelled and shown as sticks. Water-bridged hydrogen bonds between Ala47 and bases of DNA are shown as dotted yellow lines.