Figure 9.

Role of PvdO in fluorophore formation of pyoverdines and identification of functionally important residues in a potential active-site cavity of PvdO. A, biosynthetic reactions leading from ferribactin to pyoverdine via the intermediate dihydropyoverdine. PvdP is required for the initial oxidative cyclization reaction that results in the catechol system. PvdO is required for the final oxidation, resulting in the mature fluorophore. B, the two active-site residues Asp-257 and Glu-260 (red) and their position on the surface of PvdO relative to the other residues mutated in this study (blue). C (left), active-site cavity shown by the APBS (37)-calculated electrostatic potential-colored surface (scale from −10 (red) through 0 (white) to +10 (blue)). Surface-exposed side-chain regions of Asp-257 and Glu-260 are colored purple. Middle and right, superposition of the structure from FGE and PvdO_A506 structural model, highlighting the respective active-site residues at overlapping positions. The active-site Cys-272 of FGE is at exactly the same position as Glu-260 in PvdO.