Molecular model of WT EKLF bound to the β-globin promoter. (A) Overall structure of the complex. DNA is shown as an orange molecular surface; protein is shown as a gray Cα-cartoon tracing the α-carbon (Cα) atoms. The amino terminus (A278) is labeled N; the carboxy terminus (L362) is labeled C. The side chains of mutated residues are labeled and highlighted as sticks with carbon atoms colored green. (B) Close-up showing the network of hydrogen bonds formed by E325 and R328, which cannot be replicated when the glutamate side chain is replaced by lysine. All atoms are colored by atom type, with carbon atoms colored as follows: orange represents DNA; green, E325 and R328; and gray, other protein residues. Red spheres represent selected water molecules. Dashed yellow lines indicate predicted hydrogen bonds. (C) Close-up showing interactions of R331 and K332. Displayed as in panel B, except that R331 and K332 carbon atoms are colored green. (D) Close-up of K332Q model showing predicted hydrogen bonding of Q332 to DNA backbone. Displayed as in panel B, except that Q332 carbon atoms are colored green.