A low-temperature heteronuclear NMR study of two exchanging conformations of metal-bound pyoverdin PaA from Pseudomonas aeruginosa.
Under iron-deficient conditions, the Gram-negative bacterium Pseudomonas aeruginosa ATCC 15692 secretes a peptidic siderophore, pyoverdin PaA, composed of an aromatic chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and a partially cyclized octapeptide, D-Ser-L-Arg-D-Ser-L-FoOHOrn-(L-Lys-L-FoOHOrn-L-Thr-L-Thr) (FoOHOrn: delta N-formyl-delta N-hydroxyornithine), in which the C-terminal carboxyl group forms a peptidic bond with the primary amine of the L-Lys side chain. Ferric iron is chelated by the catechol group on the chromophore and the two hydroxyornithine side chains. In aqueous solution, the (1)H-NMR spectrum of pyoverdin PaA-Ga(III), in which Ga(III) is used instead of Fe(III) for spectroscopic purposes, showed clear evidence of exchange broadening, preventing further structural characterization. The use of cryo-solvents allowed measurements to be made at temperatures as low as 253 K where two distinct conformations with roughly equivalent populations could be observed. (13)C and (15)N labeling of pyoverdin PaA enabled complete assignment of both forms of pyoverdin PaA-Ga(III) at 253 and 267 K, using triple-resonance multidimensional NMR experiments commonly applied to doubly labeled proteins.
Tzou
Der-Lii
DL
Institute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan, Republic of China.
Wasielewski
Emeric
E
Abdallah
Mohamed A
MA
Kieffer
Bruno
B
Atkinson
R Andrew
RA
D002247:Carbon Isotopes; D003080:Cold Temperature; D003470:Culture Media / Q000737:chemistry; D005708:Gallium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism*; D000090463:Iron Deficiencies; D007700:Kinetics; D008968:Molecular Conformation; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D011522:Protons; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development; D017262:Siderophores / Q000032:analysis / Q000737:chemistry
D002247:Carbon Isotopes; D003470:Culture Media; D009587:Nitrogen Isotopes; D009842:Oligopeptides; D011522:Protons; D017262:Siderophores; C042453:pyoverdin; D005708:Gallium; D007501:Iron