The modeled structures of the regulatory polypeptides of the native E. coli (in red), native S. marcescens (in purple), chimera SM : rS5′ec (in blue) and EC : rS5′sm (in green) enzymes display the overlapping and separation of the backbones and the relocation of the side-chains. A, The superimposed regulatory polypeptides of the four enzymes; B, The superimposed regulatory polypeptides of the native E. coli (in red) and EC : rS5′sm chimera (in green); and C, the superimposed regulatory polypeptides of the native S. marcescens (in purple) and SM : rS5′ec chimera (in blue) enzymes.