FIGURE 1.

Pyoverdine maturation by periplasmic enzymes and their genetic relatedness. A, postulated structure of PVD_A506 (24), showing the fluorophore and the position of the modified N-terminal residue (R₁), which are the regions where periplasmic maturation occurs. The three shown R₁ side chains represent the three structures that are relevant in this study. B, conserved clustered organization of the pvdMNO operon and the pvdP gene, which encode the periplasmic pyoverdine maturation enzymes. PvdQ, which has also functions in other pathways, is not encoded in this cluster.