The downfield resonances in the 1H NMR spectra of Azotobacter vinelandii and Pseudomonas putida seven-iron ferredoxins.
J Biol Chem
; 265(21): 12388-92, 1990 Jul 25.
Article
en En
| MEDLINE
| ID: mdl-2373698
ABSTRACT
Pseudomonas putida and Azotobacter vinelandii ferredoxins each contain one [4Fe-4S] cluster and one [3Fe-4S] cluster. Their polypeptide chains are nearly identical, differing by only 15 residues out of a total of 106. T1 measurements and temperature dependence studies of the 1H NMR spectrum of each ferredoxin demonstrate that all six resolved downfield resonances are near an iron-sulfur center. The five most downfield resonances are shown to arise from protons on cysteinyl beta-carbons by incorporation of cysteine deuterated at the beta-carbon into cell protein. The sixth peak (10.5 ppm) is shown to be a non-cysteinyl proton. This peak resolves into two resonances of approximately equal intensity at temperatures below 15 degrees or above 25 degrees C. A nuclear Overhauser effect observed between the two downfield-most resonances of A. vinelandii ferredoxin indicates that they originate from a geminal pair of beta-cysteinyl protons. An Overhauser effect observed between the resonances at 22.3 and 15.7 ppm, in conjunction with other results, implies that the resonance at 22.3 ppm arises from a beta-proton on the 3Fe-center-bound Cys16, while the resonance at 15.7 ppm arises from Cys45 beta-proton, which is bound to the 4Fe center. The five most downfield resonances are pH-dependent. The sixth peak (10.5 ppm in P. putida ferredoxin) is pH-independent. Possible origins for the observed pH dependencies are discussed.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Pseudomonas
/
Azotobacter
/
Ferredoxinas
Idioma:
En
Revista:
J Biol Chem
Año:
1990
Tipo del documento:
Article
Pais de publicación:
EEUU
/
ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
/
EUA
/
UNITED STATES
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UNITED STATES OF AMERICA
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US
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USA