Fig 3. Fdc^UbiX cofactor structure and ligand complexes.

a) Omit electron density map corresponding to a distinct isomer of the prFMN contoured 5 sigma. An expansion of the central ring of the isoalloxazine system can clearly be observed, with the distinct butterfly-bent conformation accompanied by altered conformation of the ribityl moiety. b) Detailed view of prFMN^ox isoforms in the Fdc^UbiX-substrate complexes. The omit electron density maps corresponding respectively to the prFMN^iminium (in blue) and prFMN^ketimine (in red) species each contoured 5 sigma are shown for the alpha-methyl-cinnamic acid complex. c) A series of Fdc^UbiX substrate/product complexes. Selected active site residues of Fdc^UbiX are shown in atom colour sticks, with the omit electron density contoured at 5 sigma corresponding to respectively alpha-methyl-cinnamic acid, pentafluorocinnamic acid, alpha-fluorocinnamic acid and 4-vinyl-guaiacol.