We have investigated the subcellular location of nitrate reductase in Chlorella. Chlorella is a unicellular green algae. The algae can be readily cultured under defined conditions. When cultures of Chlorella are grown in media containing ammonia, as a nitrogen source, there is a very low activity of nitrate reductase. If cultures are are grown in the absence of ammonia, but with nitrate substituted as a nitrogen source, the activity of the enzyme increases about ten-fold. This increase is dependent on protein synthesis and is inhibited by cycloheximide.Nitrate reductase was purified to homogeneity and injected into rabbits. Antinitrate reductase IGg was prepared and used to localize the enzyme in the light microscope with FITC conjugated goat anti-rabbit IGg and electron microscope with goat anti-rabbit IGg coupled to colloidal gold.Samples of ammonia and nitrate grown cultures were fixed in gluteral- dehyde and embedded in polyethylene glycol. Thick and thin sections were cut for light and electron microscope localization according to Wolosowick and May.
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