Document Detail


Purification and characterization of a ferredoxin from Rhizobium japonicum bacteroids.
MedLine Citation:
PMID:  6246115     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
An eight-iron, eight-sulfur ferredoxin from Rhizobium japonicum bacteroids of soybean root nodules has been purified to apparent homogeneity as judged by disc gel electrophoresis. The purification procedure included chromatography on DEAE-cellulose, Bio-Gel P-60, and hydroxylapatite. Specific activities of several purified preparations of bacteroid ferredoxin ranged from 1700 to 1900 nmol of C2H4 produced . min-1 . mg-1 in the reaction mediating electron transfer between illuminated chloroplasts and bacteroid nitrogenase. A molecular weight of 6740 for the protein was determined by low speed sedimentation equilibrium and a molecular weight of 6500 was estimated from the mobility of bacteroid ferredoxin relative to the mobility of standard proteins during sodium dodecyl sulfate disc gel electrophoresis. All of the common amino acids were present except arginine, methionine, and tryptophan. The absorbance spectrum of the oxidized protein exhibited maxima at 285 nm and 380 nm with a shoulder near 305 nm. The A380/A285 ratio was 0.76 and the extinction coefficient at 380 nm for the oxidized protein was found to be 30,800 M-1. Equilibration of bacteroid ferredoxin with methyl viologen at various potentials revealed a midpoint oxidation-reduction potential of -484 mV. Spectrophotometric examination of iron-sulfur clusters extruded from bacteroid ferredoxin with benzenethiol and the transfer of its iron-sulfur clusters to other ferredoxins established the presence of two [4Fe-4S] clusters in a molecule of bacteroid ferredoxin. The EPR spectrum of oxidized ferredoxin consisted of a small signal at g = 2.02 integrating to 0.19 spin/molecule. The EPR spectrum of ferredoxin reduced with 5-deazaflavin exhibited a signal with features at g values of 1.88, 1.94, 2.01, and 2.07, and integrated to 1.7 spins/molecule. The EPR properties of bacteroid ferredoxin are characteristic of a ferredoxin operating between the 1+ and 2+ oxidation levels. Bacteroid ferredoxin mediated electron transfer to clostridial hydrogenase, but was not reduced by the clostridial phosphoroclastic system in the presence of pyruvate. Bacteroid ferredoxin reduced by illuminated 5-deazariboflavin also supported a high rate of C2H2 reduction by bacteroid nitrogenase which was free of Na2S2O4. It was concluded, on this basis, that bacteroid ferredoxin has the capability of functioning as the electron donor for nitrogenase in R. japonicum.
Authors:
K R Carter; J Rawlings; W H Orme-Johnson; R R Becker; H J Evans
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  255     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1980 May 
Date Detail:
Created Date:  1980-07-22     Completed Date:  1980-07-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  4213-23     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Amino Acids / analysis
Clostridium / metabolism
Dithionitrobenzoic Acid
Electron Spin Resonance Spectroscopy
Electron Transport
Ferredoxins* / isolation & purification,  metabolism
Iron / analysis
Oxidation-Reduction
Protein Binding
Rhizobium / metabolism*
Species Specificity
Sulfides / analysis
Chemical
Reg. No./Substance:
0/Amino Acids; 0/Ferredoxins; 0/Sulfides; 69-78-3/Dithionitrobenzoic Acid; 7439-89-6/Iron

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