Observed I (blue) and the mean expected Iexp (thick red) mutual information in DNA-binding (A) and ligand-binding (B) domains of LacI family. Thin red lines show Iexp ± 2σ (Iexp). P(I) is statistical significance of mutual information. Filled circles indicated residues with I > 1.0. Positions with filled circles and low P(I) are predicted Specificity determinants. The number along the sequence are according to 1wet PDB structure.