A low-temperature heteronuclear NMR study of two exchanging conformations of metal-bound pyoverdin PaA from Pseudomonas aeruginosa
✍ Scribed by Der-Lii Tzou; Emeric Wasielewski; Mohamed A. Abdallah; Bruno Kieffer; R. Andrew Atkinson
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2005
- Tongue
- English
- Weight
- 348 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
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: δ__N__‐formyl‐δ__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. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 139–149, 2005
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