Figure 5

Domain comparison of PcrA, RecB and RecC. The structures of a) substrate-complexed PcrA (PDB code 3pjr; [38]), b) RecB and c) RecC (PDB code 1w36; [18]), are superimposed using domain 2A. The domains 1A are coloured red, while orange is used for 1B, blue for 2A, cyan for 2B, green for 3 and yellow for 4. The same colours are used in the schematic diagram d) which illustrates how evolution progressed through addition of domains. The "pin" and "hoop" in RecC (see text for details) are labelled. In PcrA the residues defining the starts of the various (sub-)domains are 1B, 92; 1A continuation, 218; 2A, 287; 2B, 385; 2A continuation, 553. In RecB the corresponding residue numbers are 1B, 151; 1A continuation, 349; 2A, 446; 2B, 583; 2A continuation, 729; linker, 870; 3, 900. In RecC they are 1B, 79; 1A continuation, 208; 2A, 329; 2B, 443; 2A continuation, 649; linker, 784; 3, 828; 4, 1034.