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The E. coli cAMP Receptor Protein (CRP, a.k.a. CAP) is a transcriptional activator that binds to DNA (shown using the Spacefill display with yellow backbone). The two subunits of the symmetric dimer are shown using the Backbone display; the cAMP-binding domain is blue and the DNA-binding domain is purple. The cAMP molecules bound to each subunit are shown as Spacefill with CPK coloring. (cf. Fig. 2 of Schultz, et al.)
Close-up view of protein-DNA interactions in one half-site.
    Amino acid sidechains H-bond to the DNA bases as follows: Arg180 to G7; Glu181 to C5; and Arg185 to G5.
    The helix-turn-helix (HTH) motif is colored magenta within the purple DNA-binding domain. (cf. Fig. 3B of Schultz, et al.)

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