Atp hydrolysis and electron transfer in the nitrogenase reaction with different combinations of the iron protein and the molybdenum-iron protein

Ljones, Torbjørn; Burris, R. H.

doi:10.1016/0005-2728(72)90027-8

Cited by 93 publications

(51 citation statements)

References 19 publications

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“…3 The next step in FeMo-co biosynthesis involves NifH. NifH has been shown to be a multifunctional "moonlighting" protein (34) playing diverse roles in the nitrogenase enzyme system: 1) substrate reduction wherein it functions as the obligate electron donor to dinitrogenase (35); 2) the maturation of apodinitrogenase wherein its presence is required for associating NafY with the NafY-deficient apodinitrogenase (36); and 3) the biosynthesis of FeMo-co (8,26,37). Its role in substrate reduction is best understood, while the specific role(s) of NifH in the latter two processes is obscure.…”

Section: Incorporation Of 99 Mo Into Components Of the In Vitro Femo-mentioning

confidence: 99%

Accumulation of 99Mo-containing Iron-Molybdenum Cofactor Precursors of Nitrogenase on NifNE, NifH, and NifX ofAzotobacter vinelandii

Rangaraj

Ludden

2002

Journal of Biological Chemistry

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Section: Incorporation Of 99 Mo Into Components Of the In Vitro Femo-mentioning

confidence: 99%

Accumulation of 99Mo-containing Iron-Molybdenum Cofactor Precursors of Nitrogenase on NifNE, NifH, and NifX ofAzotobacter vinelandii

Rangaraj

Ludden

2002

Journal of Biological Chemistry

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“…During this process, which occurs at substantial rates even when nitrogen is saturating (11,12), about four molecules of ATP are 1207 hydrolyzed per H2 produced (13)(14)(15). Although H2 evolution has been observed from detached nodules of some legumes (16)(17)(18)(19)(20), it has been suggested that no net ATP-dependent production of hydrogen via nitrogenase occurs in vivo (5).…”

Section: Introductionmentioning

confidence: 99%

“…There are reports (15,29) that the extent of hydrogen evolution in vitro varies with energy charge and that energy charge in nodules was affected by the rate of photosynthesis (30). It was considered necessary, therefore, to measure hydrogen production by intact nodulated soybean cultures under conditions where shoots were exposed to light and 4 TIME (hr) FIG.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen evolution: A major factor affecting the efficiency of nitrogen fixation in nodulated symbionts

Schubert

Evans

1976

Proc. Natl. Acad. Sci. U.S.A.

446

276

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Nitrogenase-dependent hydrogen evolution from detached legume nodules and from reaction mixtures containing cell-free nitrogenase has been well established, but the overall effect of hydrogen evolution on the efficiency of nitrogen fixation in vivo has not been critically assessed. This paper describes a survey which revealed that hydrogen evolution is a general phenomenon associated with nitrogen fixation by many nodulated nitrogen-fixing symbionts. An evaluation of the magnitude of energy loss in terms of the efficiency of electron transfer to nitrogen, via nitirogenase, in excised nodules suggested that hydrogen production may severely reduce nitrogen fixation in many legumes where photosynthate supply is a factor limiting fixation. With most symbionts. including soybeans, only 40-60% of the electron fow to nitrogenase was transferred to nitrogen. The remainder was lost through hydrogen evolution. In situ measurements of hydrogen evolution and acetylene reduction by nodulated soybeans confirmed the results obtained with excised nodules. In an atmosphere of air, a major portion of the total electron flux available for the reduction of atmospheric nitrogen by either excised nodules or intact nodulated plants was utilized in the production of hydrogen gas. Some nonleguminous symbionts, such as Alnus rubra, and a few legumes (i.e., Vigns sinensis) apparently have evolved mechanisms of minimizing net hydrogen production, thus increasin their efficiency of electron. transfer to nitrogen. Our res ts indicate that the extent of hydrogen evolution during nitrogen reduction is a major factor affecting the efficiency of nitrogen fixation by many agronomically important legumes. The increasing world population and depletion of fossil fuel supplies have stimulated renewed interest in methods of increasing agricultural productivity while minimizing the consumption of fossil fuels. A major factor limiting agricultural production is nitrogen fertilizer, the synthesis of which consumes major quantities of energy. Approximately 3% (600 X 109 cubic feet; 16.8 X 109 meter3) of the natural gas consumed in the United States in 1973 was used for the synthesis of 17 X 106 U.S. tons (153 X 108 kg) of anhydrous ammonia (1, 2). About 10 X 106 U.S. tons of synthetic ammonia were used for nitrogen fertilizer to supply a portion of an annual agricultural nitrogen demand of about 18 X 106 U.S. tons (1, 2). A large part of the remaining need for nitrogen in agriculture was supplied by nitrogen-fixing organisms, such as legumes, which utilize photosynthetically stored solar energy to reduce atmospheric nitrogen to ammonia. Because the biological nitrogen-fixing process is not dependent upon nonrenewable energy resources, its use in agriculture should be maximized. Factors limiting biological nitrogen fixation therefore deserve thorough investigation (3,4).One characteristic of all cell-free nitrogenase preparations that might limit nitrogen fixation is the release of hydrogen gas concomitant with nitrogen reduction (5-11). During thi...

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“…ATP is not hydrolyzed to adenosine 5'-diphosphate until component II transfers an electron to component I (161). There seem to be two ATPs hydrolyzed for each electron transferred (127). However, ATP hydrolysis can be uncoupled from electron transfer.…”

Section: Biochemistry Nitrogenasementioning

confidence: 99%

“…However, ATP hydrolysis can be uncoupled from electron transfer. For instance, an excess of component I leads to a higher ratio of ATP to electrons transferred (127). In vivo, a constant ratio of these two components is maintained by having the three structural genes (in K. pneumoniae, at least) being part of a single operon, nifHDK (134,142 (97) and 20 ATPs are required in C. pasteurianum (49).…”

Section: Biochemistry Nitrogenasementioning

confidence: 99%

Biochemical Genetics of Nitrogen Fixation

Brill¹

1983

Structure and Function of Plant Genomes

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Atp hydrolysis and electron transfer in the nitrogenase reaction with different combinations of the iron protein and the molybdenum-iron protein

Cited by 93 publications

References 19 publications

Accumulation of 99Mo-containing Iron-Molybdenum Cofactor Precursors of Nitrogenase on NifNE, NifH, and NifX ofAzotobacter vinelandii

Accumulation of 99Mo-containing Iron-Molybdenum Cofactor Precursors of Nitrogenase on NifNE, NifH, and NifX ofAzotobacter vinelandii

Hydrogen evolution: A major factor affecting the efficiency of nitrogen fixation in nodulated symbionts

Biochemical Genetics of Nitrogen Fixation

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