Molecular basis of pyoverdine siderophore recycling in Pseudomonas aeruginosa.
The siderophore pyoverdine (PVD) is a primary virulence factor of the human pathogenic bacterium Pseudomonas aeruginosa, acting as both an iron carrier and a virulence-related signal molecule. By exploring a number of P. aeruginosa candidate systems for PVD secretion, we identified a tripartite ATP-binding cassette efflux transporter, here named PvdRT-OpmQ, which translocates PVD from the periplasmic space to the extracellular milieu. We show this system to be responsible for recycling of PVD upon internalization by the cognate outer-membrane receptor FpvA, thus making PVD virtually available for new cycles of iron uptake. Our data exclude the involvement of PvdRT-OpmQ in secretion of de novo synthesized PVD, indicating alternative pathways for PVD export and recycling. The PvdRT-OpmQ transporter is one of the few secretion systems for which substrate recognition and extrusion occur in the periplasm. Homologs of the PvdRT-OpmQ system are present in genomes of all fluorescent pseudomonads sequenced so far, suggesting that PVD recycling represents a general energy-saving strategy adopted by natural Pseudomonas populations.
Imperi
Francesco
F
Department of Biology, University Roma Tre, Viale G. Marconi 446, 00146 Roma, Italy.
Tiburzi
Federica
F
Visca
Paolo
P
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D007700:Kinetics; D018613:Microscopy, Confocal; D008954:Models, Biological; D009842:Oligopeptides / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C082326:FpvA protein, Pseudomonas aeruginosa; D009842:Oligopeptides; D017262:Siderophores; D037521:Virulence Factors; C042453:pyoverdin