Effects of homocitrate, homocitrate lactone, and fluorohomocitrate on nitrogenase in NifV- mutants of Azotobacter vinelandii. |
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Authors: | M S Madden T D Paustian P W Ludden V K Shah |
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Affiliation: | Department of Biochemistry, University of Wisconsin-Madison 53706. |
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Abstract: | Azotobacter vinelandii DJ71, which contains a mutation in the nifV gene, was derepressed for nitrogenase in the presence of homocitrate. When dinitrogenase was isolated from this culture, it was found to be identical to the wild-type dinitrogenase. However, when the same NifV- strain was derepressed in the presence of erythrofluorohomocitrate, a homocitrate analog which produces a nitrogenase with wild-type properties in vitro, the isolated dinitrogenase was characteristic of the NifV- enzyme. These data show that homocitrate, but not fluorohomocitrate, is utilized by NifV- mutant cells. Fluorohomocitrate does not inhibit the uptake of homocitrate because the wild-type phenotype resulted when both compounds were added to the medium during nitrogenase derepression. Homocitrate lactone failed to cure the NifV- phenotype. |
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