Studies on a Novel Flavodoxin from the Respiratory Mutant TZN-200 from Azotobacter Vinelandii
Flavodoxins have been purified from the wild-type and mutant strain TZN-200 of A. vinelandii. The latter mutant strain is unable to reduce 2,3,5-triphenyl-tetrazolium chloride which is known to react with flavin. As a consequence FMN synthesized in the mutant strain appears to be modified as determined by paper chromatography and light-absorption spectroscopy. The mutant flavodoxin does not differ from the wild-type derived flavodoxin in primary structure as determined by partial peptide mapping or by Resonance Coherent Anti-Stokes Raman Spectroscopy which suggests binding of FMN to protein is identical in both flavodoxins. However significant differences were noted in the ability of the mutant flavodoxin to donate electrons to nitrogenase (decreased by 75%). This latter observation may be explained by the more positive mid-point redox potential found for the flavosemiquinone/flavohydroquinone redox couple (-435 mV as compared to the same redox couple for wild type flavodoxin of -480 mV).
KeywordsMutant Strain Ammonium Sulfate Redox Couple Ammonium Sulfate Gradient Flavin Moiety
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