Nitrate reduction, function

Moreno-Vivian C, P Cabello, M Martmez-Luque, R Blasco, F Castillo (1999) Prokaryotic nitrate reduction molecular properties and functional distinction among bacterial nitrate reductases. J Bacteriol 181 6573-6584. 

Nitrate reduction in higher plants molecular approaches to function and regulation... 

Relatively recently Fe/S proteins have been found to function in the regulation of biosynthesis. This can be by promoting deoxyribonucleic acid (DNA) transcription, e.g. the [2Fe-2S] containing Escherichia coli superoxide-activated (SoxR) transcription activator [10-12], or the presumably [4Fe-4S]-containing E. coli transcription factor fumarate nitrate reduction (FNR) [13,14], Alternatively, the Fe/S protein can act by interference with messenger ribonucleic acid (mRNA) translation, i.e., the iron regulatory proteins (IRPs) [15,16], These interactions are stoichiometric, therefore not catalytic. Presumably, they are also a form of sensoring, namely, of oxidants and/or iron [17],... 

Molybdenum is essential to the formation and activity of assimila-tory nitrate reductases. Cells must assimilate molybdate from the environment, metabolize molybdenum in some manner to form active molybdenum cofactor, and then incorporate it into a large molecular weight protein so that it can perform a reversible redox reaction with nitrate. Investigations on the aqueous Mo (III) model systems for nitrate reduction and the coordination of molybdate by naturally produced phenolates will hopefully lead to an understanding of the complex process of molybdenum acquisitions by and molybdenum function in nitrate reductases. 

E. coli, under anaerobic conditions, when nitrate is the electron acceptor, Q is the preferred quinone. But in the absence of MK can substitute for this function. However, under anaerobic conditions when fumarate, trimethylamine A -oxide (TMAO), dimethylsulfoxide (DMSO), or tetrahydrothiophene 1-oxide (THTO) serve as the electron acceptors, the presence of MK is obligatoryReconstitution studies using membrane preparations from quinone-deficient strains suggest that MK is specifically involved in fumarate and DMSO reduction, while either MK or DMK can function in TMAO reduction, and that nitrate reduction requires either Q or MK. ... 

Metal ions play an important role in nitrate reduction. The discovery and characterization of the pyridine nucleotide enzymes involved in nitrate reduction (20AI8,20A65,20A81, 20A83) made it possible to understand the role of mineral ions in the nitrate reduction processes. Reduced pyridine nucleotides and flavin adenine dinucleotide function as cofactors in reduction of nitrate, nitrite, hyponitrate, and hydroxylam-ine. The first step of the reaction involves the reduction of nitrate to nitrite, and Mo is essential for this reaction. The reduction of nitrite to hyponitrite and hyponitrite to hydroxy-lamine requires Cu and Fe ions (20A20). 

Another example of this type of regulatory function of iron-sulfur-containing proteins can be found in the transcription factor FNR (/umarate nitrate reduction). 

GTP = 5 -guanosine triphosphate AE = Activating enzyme BAN = Backbone amide nitrogen BioB = Biotin synthase CD = Circular dichroism cyt = Cytochrome DFT = Density functional theory DMSO = Dimethylsulfoxide Dx = Desulforedoxin ENDOR = Electron-nuclear double resonance EPR = Electron paramagnetic resonance ESEEM = Electron-spin echo envelop modulation ETF = Electron transferring flavoprotein EXAFS = Extended x-ray absorption fine structure FAD = Flavin adenine dinucleotide Fd = Ferredoxin FMN = Flavin mononucleotide FNR = Fumarate-nitrate reduction FTIR =... 

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