DNA binding specificity of the Arc and Mnt repressors is determined by a short region of N-terminal residues.

The Arc and Mnt repressors of phage P22 are related proteins that bind to different operator DNA sites. By creating a hybrid Arc-Mnt protein, we show that the binding specificity of Mnt can be switched to that of Arc by replacing six residues at the N terminus of Mnt with the corresponding nine residues from Arc.