The biosynthesis of nitrogenase MoFe protein polypeptides in free-living cultures of Rhizobium japonicum.
The biosynthesis of the constituent polypeptides of nitrogenase component I (Rj 1) in free-living cultures of Rhizobium japonicum (strain 110) was investigated under different growth conditions. Cells were pulse-labelled and the proteins analysed by one and two-dimensional gel electrophoresis. The positions of the constituent Rj 1 polypeptides were identified by co-electrophoresis with purified Rj 1 isolated from bacteroids of soybean nodules, and by comparison with an immunoprecipitate from a culture induced for nitrogenase. The synthesis of the proteins preceded any detectable enzyme activity and increased with time, reaching a maximum after 3 days. At this time, between 6 and 8% of the total sodium dodecyl sulfate-soluble protein synthesized was Rj 1. Exposure to air led to a dramatic decrease in the rate of Rj 1 synthesis, with almost complete regression after 20 min. In the presence of KNO3, there was no nitrogenase activity, but the proteins were present in similar amounts (7%) as the control culture. When mannitol and glycerol were used as the sole carbon sources, the amount of Rj 1 synthesized was extremely low.
D005942:Gluconates / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology; D009591:Nitrogenase / Q000096:biosynthesis*; D010100:Oxygen / Q000494:pharmacology; D010452:Peptide Biosynthesis; D012231:Rhizobium / Q000201:enzymology*
D005942:Gluconates; D005971:Glutamates; D009566:Nitrates; D008353:Mannitol; D009591:Nitrogenase; D005990:Glycerol; D010100:Oxygen