FIGURE 4.

PvdN is responsible for a pyoverdine modification. A, isoelectric focusing indicates that wild type P. fluorescens A506 produces two pyoverdines, whereas the ΔpvdN mutant strain can only form one pyoverdine species (left gel). Besides the wild type and mutant strains, the IEF gel also shows the pyoverdines of strains with complementation vectors that contain either a wild type pvdN gene or a gene encoding the protein with a K261A mutation. Note the functional complementation by the wild type pvdN gene, whereas the exchange of the active site lysine completely abolishes the activity. The CAS overlay assay of the same IEF gel demonstrates the iron binding capacity of both pyoverdines (right gel). B, analysis of pyoverdine content in wild type P. fluorescens A506 and its ΔpvdN mutant. Left and right, reverse phase chromatography elutions (left) and corresponding mass spectra (right) of the succinamide and α-ketoglutarate forms of the pyoverdine (numbers correspond to structures in Fig. 1A). The elution profiles monitor the respective molecular masses during reverse phase chromatography, indicated beside the y-axes, showing that no succinamide is formed by the ΔpvdN mutant.