scholarly journals Evidence for an alternative nitrogen fixation system in Azotobacter vinelandii.

1980 ◽  
Vol 77 (12) ◽  
pp. 7342-7346 ◽  
Author(s):  
P. E. Bishop ◽  
D. M. Jarlenski ◽  
D. R. Hetherington
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Fixation System

The flavin transferase ApbE flavinylates the ferredoxin:NAD+-oxidoreductase Rnf required for N2 fixation in Azotobacter vinelandii

2021 ◽  
Author(s):  
Yulia V Bertsova ◽  
Marina V Serebryakova ◽  
Alexander A Baykov ◽  
Alexander V Bogachev
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Growth Defect ◽  
Deficient Mutant ◽  
Fixed Nitrogen ◽  
Oxidoreductase Activity ◽  
Threonine Residue ◽  
Ferredoxin Reductase ◽  
Relative Contribution ◽  
Fixation System

Abstract Azotobacter vinelandii, the model microbe in nitrogen fixation studies, uses the ferredoxin:NAD+-oxidoreductase Rnf to regenerate ferredoxin (flavodoxin) acting as an electron donor for nitrogenase. However, the relative contribution of Rnf into nitrogenase functioning is unknown because this bacterium contains another ferredoxin reductase, FixABCX. Furthermore, Rnf is flavinylated in the cell, but the importance and pathway of this modification reaction also remain largely unknown. We have constructed A. vinelandii cells with impaired activities of FixABCX and/or putative flavin transferase ApbE. The ApbE-deficient mutant could not produce covalently flavinylated membrane proteins and demonstrated a markedly decreased flavodoxin:NAD+ oxidoreductase activity and significant growth defect under diazotrophic conditions. The double ΔFix/ΔApbE mutation abolished the flavodoxin:NAD+ oxidoreductase activity and the ability of A. vinelandii to grow in the absence of fixed nitrogen source. ApbE flavinylated a truncated RnfG subunit of Rnf1 by forming a phosphoester bond between FMN and a threonine residue. These findings indicate that Rnf (presumably its Rnf1 form) is the major ferredoxin-reducing enzyme in the nitrogen fixation system and that the activity of Rnf depends on its covalent flavinylation by the flavin transferase ApbE.

scholarly journals Expression of an alternative nitrogen fixation system in Azotobacter vinelandii.

1982 ◽  
Vol 150 (3) ◽  
pp. 1244-1251 ◽  
Author(s):  
P E Bishop ◽  
D M Jarlenski ◽  
D R Hetherington
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Fixation System

Nitrogen Fixation byAzotobacter vinelandiiStrains Having Deletions in Structural Genes for Nitrogenase

Science ◽  
1986 ◽  
Vol 232 (4746) ◽  
pp. 92-94 ◽  
Author(s):  
PAUL E. BISHOP ◽  
R. PREMAKUMAR ◽  
DENNIS R. DEAN ◽  
MARTY R. JACOBSON ◽  
JOHN R. CHISNELL ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Molecular Nitrogen ◽  
Phenotypic Expression ◽  
Structural Genes ◽  
Reversal Phenomenon ◽  
Molybdenum Enzyme ◽  
Phenotypic Reversal ◽  
Free Media ◽  
Fixation System

Phenotypic reversal of Nif-mutant strains to Nif+under molybdenum-deficient conditions has been cited as evidence thatAzotobacter vinelandiipossesses two nitrogen fixation systems: the conventional molybdenum-enzyme system and an alternative nitrogen-fixation system. Since explanations other than the existence of an alternative system were possible, deletion strains ofA. vinelandiilacking the structural genes for conventional nitrogenase (nifHDK) were constructed. These strains were found to grow in molybdenum-deficient nitrogen-free media, reduce acetylene (at low rates), and incorporate molecular nitrogen labeled with nitrogen-15. Thus it can be concluded that the phenotypic reversal phenomenon cannot be due to altered phenotypic expression ofnifmutations under molybdenum-deficient conditions, but is due to the existence of an alternative nitrogen-fixation system inA. vinelandiias originally proposed.

Nitrogen fixation by cell-free extracts of Klebsiella pneumoniae

1968 ◽  
Vol 14 (1) ◽  
pp. 33-38 ◽  
Author(s):  
M. C. Mahl ◽  
P. W. Wilson
Keyword(s):  
Nitrogen Fixation ◽  
Klebsiella Pneumoniae ◽  
Azotobacter Vinelandii ◽  
Ammonium Ion ◽  
Michaelis Constant ◽  
Nitrogen Gas ◽  
Aerobacter Aerogenes ◽  
Free System ◽  
Evolving System ◽  
A Cell

A cell-free system which permits nitrogen fixation by extracts of Klebsiella pneumoniae M5al (formerly Aerobacter aerogenes) has been developed. It is, essentially, that system described by Bulen and associates for Azotobacter vinelandii, utilizing ATP as a source of energy and dithionite as a source of electrons. The Michaelis constant for fixation has been estimated to be 0.12 atm. The extracts possessed an ATP-dependent hydrogen evolving system. Hydrogen evolution from these extracts was less under nitrogen than under helium in the presence of ATP. Nitrogen gas appears to be the inducer of nitrogen fixation. In the absence of N2, no induction of nitrogenase occurs. Nitrogenase is absent in cells grown on NH4+-N. There is a lag of about 13 h after the introduction of N2 gas into a culture which has depleted its supply of NH4+-N before nitrogenase can be detected. For reasons discussed in the text, this conclusion must be regarded as tentative at this time. Ammonium ion appears to prevent the synthesis of new molecules of nitrogenase without affecting the activity of those already formed.

Three Nitrogen Fixation Systems in Azotobacter vinelandii

1990 ◽  
pp. 52-60 ◽  
Author(s):  
P. E. Bishop ◽  
R. D. Joerger ◽  
R. Premakumar
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii
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