Expression nitrite reductase

Back, E., Dunne, W., Schneiderbauer, A., de Framond, A., Rastogi, R. Rothstein, S.J. (1991). Isolation of the spinach nitrite reductase gene promoter which confers nitrate inducibility on GUS gene expression in transgenic tobacco. Plant Molecular Biology 17, 9-18. 

Faure, J.D., Vincentz, M., Kronenberger, J. Caboche, M. (1991). Co-regulated expression of nitrate and nitrite reductases. The Plant Journal 1, 107-13. 

Intriguingly, the blue copper sites, especiaUy those with a carbonyl oxygen at the axial coordination position, display high affinity for Zn + ions. Mutants in which the Met is replaced by Gin or Glu preferentiaUy bind Zn + when expressed in heterologous systems, e.g., Escherichia coli. Examples include azurin, amicyanin, nitrite reductase, and possibly also plastocyanin (Diederix et al., 2000 Hibino et al., 1995 Murphy et al., 1995 Nar et al., 1992a Romero et al., 1993). In the case of azurin it has been shown that both wild-type and the Met—Gin mutant have the same affinity for both Zn +and Cu + (Romero ci a/., 1993). In addition, EXAFS studies showed that some preparations of blue copper proteins purihed from their natural sources also contain small fractions of Zn derivatives (DeBeer George, personal communication). 

Surprisingly, its biological redox partners remain largely unknown. It has been implicated in anaerobic nitrite respiration and it has been shown that azurin can donate electrons to nitrite reductase, a function that is proposed to be carried out by another cupredoxin, pseudoazurin (see Section IV, E). On the other hand, azurin is not an inducible protein and denitrifying bacteria express azurin constitutively under aerobic conditions. 

In various species of bacteria several different types of non-assimilatory nitrite reductases are found. Escherichia coli has a cytoplasmic NAD(P)H-dependent enzyme whose role seems to be detoxification of nitrite. This type of enzyme, coded for by the nirB gene, also contains siroheme as the redox active catalytic center (Cole, 1988). Additionally in E. coli, and expressed under different conditions to the cytoplasmic enzyme, is a periplasmic nitrite reductase that catalyses formation of ammonia from nitrite (Cole, 1988). This enzyme has five c-type (Figure 1) hemes per polypeptide chain one of these hemes, the catalytic site, has the unique CXXCK sequence as its attachment site (Einsle et al., 1999). Electrons reach this type of nitrite reductase, which is fairly widely distributed amongst the microbial world, from the cytoplasmic membrane electron transfer chain. The exact electron donor partner from such chains for this type of nitrite reductase is unknown (Berks et al., 1995). 

Olesen K, Veselov A et al (1998) Spectroscopic, kinetic, and electrochemical characterization of heterologously expressed wild-type and mutant forms of copper-containing nitrite reductase fi om Rhodobacter sphaeroides 2.4.3. Biochemistry 37 6086-6094... 

A new class of copper-containing nitrite reductases constitutes the major anaerobically induced outer membrane protein from pathogenic Neisseria gonor-rhoeae. The crystal structure of the soluble domain of this protein revealed a type-1 Cu with unusual visible absorption spectra, and a bidentate mode of nitrite binding to the type-2 Cu center [92]. In this organism, the expression of nitrite reductase appears to enhance the resistance against human sera [93]. 

In Equations (5) and (7) the system spin, S, enters the expressions for Bint at both iron sites, i.e., one spin, namely the cluster spin S, controls the hyperfine fields of the two sites. Because two Mossbauer spectra are observed for one spin system, it follows that the system must be a diiron cluster. This assertion is substantiated by determination of the EPR spin eoneentration (whieh yielded 1.06 0.1 spins/2 Fe for the present case). The strong correlation between an observed EPR signal and the associated Mossbauer spectrum can be used to eonsiderable advantage. Systematic use of this correlation led to the discovery of novel elusters and eluster assemblies, e.g., the P and M clusters of nitrogenase, [3Fe-4S] clusters, the eoupled heme 4Fe S] ehromo-phores in sulfite and nitrite reductase, and the deloealized Fe Fe dimer of Que and eollabor-ators (see below) additional examples are given below and in Beinert et alP... 

Enzyme activities are expressed as nmol/min/yg of chlorophyll, except for nitrite reductase ymoles/min/yg of chlorophyll. See Reference 23 for experimental details. 

Kramer etfl/., 1989 Wvalle eta/., 1989). Nitrite reductase mRNA was present in small amounts in uninduced leaves of both species but not in roots of maize. Induction by nitrate increased the NiR mRNA in both species and in both the roots and leaves of maize. Perhaps one of the two NiR genes present in maize is expressed constitutively in leaves (Kramer et al., 1989). The NiR mRNA induction pattern in maize (Kramer et al., 1989) is similar to the NR mRNA induction pattern in barley (Melzer et al., 1989). Nitrite reductase mRNA is rapidly induced by nitrate, reaching a peak within 5 hr and then declining to a lower level even in the presence of continued nitrate. The NiR mRNA appears to be short lived with a half-life as short as 30 min (Kramer et al, 1989). The mechanisms regulating these fluctuations in NiR mRNA are not known at this time. Nitrite was capable of limited induction of NiR mRNA in spinach leaves (Back etal, 1988), although the role of nitrite is equivocal due to Ae possibility of in vivo oxidation of nitrite to nitrate (Aslam et al, 1987). 

Anaerobic Growth. In the absence of molecular oxygen, electron flow is dependent on the availability of N-oxides that may serve as alternative electron acceptors 8,10,44, 45, 46). At the shift from oxygen limitation to anaerobiosis, the makeup of the respiratory network drastically changes. The expression of nitrate, nitrite, nitric oxide, and nitrous oxide reductases as well as of the blue copper-containing electron carrier pseudoazurin is established, and in a concerted action these terminal oxidoreductases couple the removal of electrons from the respiratory network to the reduction of the corresponding... 

Nitrate assimilation is an important process in rice regeneration. A quantitative trait loci gene encoding the ferrodoxin-nitiite reductase (NiR), an enzyme that catalyzes the reduction of nitrite to ammonium leading to the accumulation of toxic nitrite in culture media, was isolated from the high-regeneration rice strain Kasalath. The level of NiR expression in the... 

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