Escherichia coli nitrite reductase

In 1973, the first naturally occurring isobacteriochlorin, iron-containing siroheme, was isolated1 from a sulfite reductase of Escherichia coli. Later it was also discovered in sulfite and nitrite reductases of numerous bacteria and plants.2 Iron-free sirohydrochlorins (also called factor II) were discovered in vitamin B12 producing bacteria.3-4 Together with factor III. a sirohydrochlorin methylated in the 20-position, the reduced forms of factor II and factor III were identified as biosynthetic intermediates in the biosynthesis of vitamin B12.5... 

A strain of Escherichia coli produces a naphthotriazole from 2,3-diaminonaphthalene and nitrite that is formed from nitrate by the action of nitrate reductase. The initial product is NO, which is converted by reactions with oxygen into the active nitrosylating agent that reacts chemically with the amine (Ji and Hollocher 1988). A comparable reaction may plausibly account for the formation of dimethylnitrosamine by Pseudomonas stutzeri during growth with dimethylamine in the presence of nitrite (Mills and Alexander 1976) (Figure 2.2f). 

Costa, C., Macedo, A., Moura, 1., Moura, j. j. G., LeGall, J., Berber, Y., Liu, M.-Y., and Payne, W. J. (1990). Regulation of the hexaheme nitrite/nitric oxide reductase of Desulfovibrio desulfuricans, Wohnella succinogenes, and Escherichia coli. A mass spectro-metric study. FEBS Lett. 276, 67-70. 

Ji, X.-B, and Hollocher, T. C. (1989). Nitrate reductase of Escherichia coli as a NO-pro-ducing nitrite reductase. Biochem. Arch. 5, 61-66. 

A new putative member of the blue multi-copper oxidases has been isolated using the Escherichia coli yacK gene. Six copper ions per polypeptide chain were determined and assigned to two type 1 copper centers and further one type 2 and one type 3 copper. Phenoloxidase and ferroxidase properties were ascertained98 A new copper containing nitrite reductase was purified from a halophilic archaeon and the ligands to type 1 and type 2 coppers in the sequence were... 

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). 

That hydroxylamine might not be an obligatory intermediate, or occur as a free intermediate, in the reduction of nitrite to ammonia is suggested by the properties of nitrite reductases of Azotobacter chroococcum and Escherichia coli. The former is an adaptive enzyme, the formation of which requires nitrate or nitrite in the culture (31,2). It is FAD-depen-dent and presumably contains metals and p-mercuribenzoate inhibitable... 

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). 

Butt and coworkers studied the voltammetry of the (Escherichia coli) decaheme class of nitrite reductases [244] (Figure 2.13). Well-defined although unstable catalytic multi-electron voltammetric reduction of nitrite by the enzyme immobihzed on bare Au(lll) electrode surfaces is notable. The decaheme nitrite reductase is a second case for single-molecule in situ STM of a redox metalloenzyme, but image interpretation is presently not at the level for CuNiR [227]. Molecular-scale structures can be observed on the Au(lll) electrode surface under conditions where the enzyme is electrocatalytically active, with both the natural dimer and surface-dissociated monomer enzyme structures identified. Molecular conductivities (in situ STM contrasts) of the enzyme and the active enzyme-substrate states are, however, not very distinctive. 

Gwyer, J.D., Richardson, D.J., and Butt, J.N. (2006) Inhibiting Escherichia coli cytochrome c nitrite reductase voltammetry reveals an enzyme equipped for action despite the chemical challenges it may face in vivo. 

The heme c nitrite reductase was isolated from anaerobes or facultative anaerobes like Desulfovibrio desulfuricans (ATCC 27774) [128], Wolinella suc-cinogenes [129], Escherichia coli [130], two Vibrio species [131,132] and Sulfurospirillum deleyianum [133]. In D. desulfuricans (ATCC 27774), W. succi-nogenes and S.deleyianum the enzyme is membrane-bound, and in the other cases it was isolated from the soluble fraction. 

In 1973, the iron complex of sirohydrochlorin (92) was isolated from Escherichia coli, where it serves as a cofactor for sulfite reductase, Siroheme (93) also catalyzes the six electron reduction of nitrite to ammonia in nitrite reductase systems. Perhaps most remarkably of all, not only has sirohydrochlorin (92)... 

Filenko N, Spiro S, Browning DF, Squire, D, Over-ton TW, Cole J, Constantinidou C (2007) The NsrR regulon of Escherichia coli K-12 includes genes encoding the hybrid eluster protein and the peri-plasmic, respiratory nitrite reductase. J Bacteriol 189 4410 417... 

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