Pseudopaline, a staphylopine-like metallophore involved in zinc and nickel uptake in Pseudomonas aeruginosa

Metal uptake is vital for all living organisms. In metal scarce conditions, a common bacterial strategy consists in the biosynthesis of metallophores, their export in the extracellular medium and the recovery of a metal metallophore complex through dedicated membrane transporters. Staphylopine is a recently described metallophore distantly related to plant nicotianamine that contributes to the broad-spectrum metal uptake capabilities of Staphylococcus aureus . Here, we characterize a four genes operon ( PA4837 to PA4834 ) in Pseudomonas aeruginosa involved in the biosynthesis and trafficking of a staphylopine like metallophore named pseudopaline. Pseudopaline differs from staphylopine with regard to the stereochemistry of its histidine moiety associated to an alpha ketoglutarate moiety instead of pyruvate. In vivo , the pseudopaline operon is regulated by zinc through the Zur repressor. The metal uptake property of the pseudopaline system appears different from that of staphylopine with a predominant effect on nickel uptake, and on zinc uptake in metal scarce conditions mimicking a chelating environment, thus reconciling the regulation of the cnt operon by zinc with its function as a zinc importer under metal scarce conditions.