Crystal structure at high resolution of ferric-pyochelin and its membrane receptor FptA from Pseudomonas aeruginosa.
Pyochelin is a siderophore and virulence factor common to Burkholderia cepacia and several Pseudomonas strains. We describe at 2.0 A resolution the crystal structure of the pyochelin outer membrane receptor FptA bound to the iron-pyochelin isolated from Pseudomonas aeruginosa. One pyochelin molecule bound to iron is found in the protein structure, providing the first three-dimensional structure at the atomic level of this siderophore. The pyochelin molecule provides a tetra-dentate coordination of iron, while the remaining bi-dentate coordination is ensured by another molecule not specifically recognized by the protein. The overall structure of the pyochelin receptor is typical of the TonB-dependent transporter superfamily, which uses the proton motive force from the cytoplasmic membrane through the TonB-ExbB-ExbD energy transducing complex to transport ferric ions across the bacterial outer membrane: a transmembrane 22 beta-stranded barrel occluded by a N-terminal domain that contains a mixed four-stranded beta-sheet. The N-terminal TonB box is disordered in two crystal forms, and loop L8 is found to point towards the iron-pyochelin complex, suggesting that the receptor is in a transport-competent conformation.
Cobessi
David
D
Département Récepteurs et Protéines Membranaires, UMR7100 CNRS, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard Sébastien Brant, 67412 Illkirch, France. cobessi@esbs.u.strasbg.fr
Celia
Herve
H
Pattus
Franc
F
D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D007502:Iron Chelating Agents / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism; D017262:Siderophores / Q000737:chemistry* / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry* / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; C075523:FPTA protein, Pseudomonas; D007502:Iron Chelating Agents; D010636:Phenols; D011956:Receptors, Cell Surface; D017262:Siderophores; D013844:Thiazoles; C025316:pyochelin; D007501:Iron