[Specificity of binding of regulatory proteins with DNA: possible explanation in terms of "point" interactions]

On the basis of the previously obtained data on the specificity of the interactions between amino acids and nucleotide bases an attempt is undertaken to explain the origin of the specificity of binding of repressors and cro proteins to corresponding operator DNA sequences in phages lambda and P22. The rules describing the interactions between amino acids and bases are supposed to be the same for the binding of different proteins to DNA. The suggested consideration, based on the known crystallographic data as well, allows to describe the specific binding of studied regulatory proteins to operators, the absence of their binding to other DNA sequences and the decrease of their affinity to the operator sites due to the mutations.