Biosynthesis of the pyoverdine siderophore of Pseudomonas aeruginosa involves precursors with a myristic or a myristoleic acid chain

Pyoverdine I (PVDI) is the major siderophore produced by Pseudomonas aeruginosa to import iron. Biosynthesis of this chelator involves non-ribosomal peptide synthetases and other enzymes. PvdQ is a periplasmic enzyme from the NTN hydrolase family and is involved in the final steps of PVDI biosynthesis. A pvdQ mutant produces two non-fluorescent PVDI precursors with a higher molecular mass than PVDI. In the present study, we describe the use of mass spectrometry to determine the structure of these PVDI precursors and show that they both contain a unformed chromophore like ferribactin, and either a myristic or myristoleic chain that must be removed before PVDI is secreted into the extracellular medium.

► We solve by mass spectrometry the structure of two pyoverdine siderophore precursors.
► A PvdQ mutant produces these precursors.
► They both have a higher molecular mass as the pyoverdine.
► We show that both compounds contain an unformed chromophore and a myristic or a myristoleic acid chain.