Effect of N oxyanions on anaerobic induction of nitrate reductase in subcellular fractions of Bradyrhizobium sp. (Lupinus) |
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Authors: | Władysław Polcyn Robert Luciński |
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Affiliation: | (1) Institute of Experimental Biology, A. Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland |
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Abstract: | Anaerobic induction of nitrate reductase in subcellular fractions of Bradyrhizobium sp. strain USDA 3045 showed fivefold increase of the enzyme activity in spheroplasts, considered as the source of intact-membrane-bound nitrate reductase, within a 3 h time frame after nitrate addition. Such a dynamics was confirmed at the protein level, with antibodies specific to membrane-bound nitrate reductase. Nitrate reductase activity in the periplasm was one order of magnitude lower and significant only at initial 3 h of induction, within a narrow range of nitrate added. Nitrite induced the membrane-bound nitrate reductase at least 70% as effectively as nitrate, as judged from its activity pattern and Western blot analysis. The limited ability of Bradyrhizobium sp. to dissimilate ≥5 mM nitrate is not due to direct inhibition of respiratory nitrate reductase by accumulated nitrite. Moreover, a synergistic induction of membrane-bound nitrate reductase by nitrate and nitrite was indicated due to a twofold higher protein synthesis after simultaneous addition of these N oxyanions than when they were given separately. |
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Keywords: | Bradyrhizobium sp. (Lupinus) Membrane-bound nitrate reductase Nitrate and nitrite induction Nitrate respiration |
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