Proposed α-helical super-secondary structure associated with protein-DNA recognition

Knowledge of the three-dimensional structure of the bacteriophage λ Cro repressor, combined with an analysis of amino acid sequences and DNA coding sequences for this and other proteins that recognize and bind specific base sequences of double-helical DNA, suggests that a portion of the structure of the Cro repressor that is involved in DNA binding also occurs in the Cro protein from bacteriophage 434, the cII protein from bacteriophage λ, the Salmonella phage P22 c2 repressor and the cI repressor from bacteriophage λ. This α-helical super-secondary structure may be a common structural motif in proteins that bind double-helical DNA in a base sequence-specific manner.