title: The presence of ADP-ribosylated Fe protein of nitrogenase in Rhodobacter capsulatus is correlated with cellular nitrogen status.
abstract: The photosynthetic bacterium Rhodobacter capsulatus has been shown to regulate its nitrogenase by covalent modification via the reversible ADP-ribosylation of Fe protein in response to darkness or the addition of external NH4+. Here we demonstrate the presence of ADP-ribosylated Fe protein under a variety of steady-state growth conditions. We examined the modification of Fe protein and nitrogenase activity under three different growth conditions that establish different levels of cellular nitrogen: batch growth with limiting NH4+, where the nitrogen status is externally controlled; batch growth on relatively poor nitrogen sources, where the nitrogen status is internally controlled by assimilatory processes; and continuous culture. When cultures were grown to stationary phase with different limiting concentrations of NH4+, the ADP-ribosylation state of Fe protein was found to correlate with cellular nitrogen status. Additionally, actively growing cultures (grown with N2 or glutamate), which had an intermediate cellular nitrogen status, contained a portion of their Fe protein in the modified state. The correlation between cellular nitrogen status and ADP-ribosylation state was corroborated with continuous cultures grown under various degrees of nitrogen limitation. These results show that in R. capsulatus the modification system that ADP-ribosylates nitrogenase in the short term in response to abrupt changes in the environment is also capable of modifying nitrogenase in accordance with long-term cellular conditions.
authors: Département de Microbiologie et Immunologie, Université de Montréal, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors: A F
authors: AF
authors: Yakunin
authors: T V
authors: TV
authors: Laurinavichene
authors: A A
authors: AA
authors: Tsygankov
authors: P C
authors: PC
authors: Hallenbeck
mesh_terms: D003470:Culture Media; D017037:Dinitrogenase Reductase / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D009591:Nitrogenase / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000254:growth & development
chemical_list: D003470:Culture Media; D017037:Dinitrogenase Reductase; D018698:Glutamic Acid; D009591:Nitrogenase; D011065:Poly(ADP-ribose) Polymerases; D009584:Nitrogen