Minor Groove Insertion of Scr Residues His−12 and Arg3 in fkh250. (A) Electron densities for Arg3 and His−12 in the fkh250 complex. (B) Details of the His−12–Arg3 interaction and water-mediated interactions with Thy14, Thy29, and Thy30 of fkh250.
Although the basic structure of the double helix has been known since the classic work of Watson and Crick. it has become increasingly clear that the helix is not regular and that its shape depends on nucleotide sequence. In two recent papers in Cell and Nature, Barry Honig, Richard Mann and their colleagues in C2B2 and the Department of Biochemistry and Molecular Biophysics have shown that sequence-dependent variations in the helix shape allow DNA-binding proteins to recognize their specific binding sites.