Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 106, Issue 48, Pages 20440-20445Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0908760106
Keywords
ATP-binding-cassette transporter; periplasm; iron; fluorescent Pseudomonas; secretion
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Funding
- Ministry of University and Research of Italy [PRIN-2006]
- Italian Cystic Fibrosis Research Foundation [FFC 10/2007, FFC 8/2008]
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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.
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