Enzymes and associated electron transport systems that catalyse the respiratory reduction of nitrogen oxides and oxyanions

Berks, Ben C.; Ferguson, Stuart J.; Moir, James; Richardson, David J.

doi:10.1016/0005-2728(95)00092-5

Cited by 567 publications

(570 citation statements)

References 570 publications

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“…NosR is processed for domain translocation and membrane insertion and thereby loses a signal peptide, which includes the transmembrane helix TM1. Hence, our data indicate that NosR has a transmembrane core of five helices flanked on both sides by hydrophilic domains, which are fewer topological elements than suggested previously (3,53). The N-terminal hydrophilic domain is periplasmic, as shown by the use of phoA reporter gene fusions with the codons for D242 and E392 (12).…”

Section: Discussionsupporting

confidence: 50%

Functional Domains of NosR, a Novel Transmembrane Iron-Sulfur Flavoprotein Necessary for Nitrous Oxide Respiration

Wunsch

Zumft

2005

J Bacteriol

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Bacterial nitrous oxide (N 2 O) respiration depends on the polytopic membrane protein NosR for the expression of N 2 O reductase from the nosZ gene. We constructed His-tagged NosR and purified it from detergentsolubilized membranes of Pseudomonas stutzeri ATCC 14405. NosR is an iron-sulfur flavoprotein with redox centers positioned at opposite sides of the cytoplasmic membrane. The flavin cofactor is presumably bound covalently to an invariant threonine residue of the periplasmic domain. NosR also features conserved CX 3 CP motifs, located C-terminally of the transmembrane helices TM4 and TM6. We genetically manipulated nosR with respect to these different domains and putative functional centers and expressed recombinant derivatives in a nosR null mutant, MK418nosR::Tn5. NosR's function was studied by its effects on N 2 O respiration, NosZ synthesis, and the properties of purified NosZ proteins. Although all recombinant NosR proteins allowed the synthesis of NosZ, a loss of N 2 O respiration was observed upon deletion of most of the periplasmic domain or of the C-terminal parts beyond TM2 or upon modification of the cysteine residues in a highly conserved motif, CGWLCP, following TM4. Nonetheless, NosZ purified from the recombinant NosR background exhibited in vitro catalytic activity. Certain NosR derivatives caused an increase in NosZ of the spectral contribution from a modified catalytic Cu site. In addition to its role in nosZ expression, NosR supports in vivo N 2 O respiration. We also discuss its putative functions in electron donation and redox activation.

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Section: Discussionsupporting

confidence: 50%

Functional Domains of NosR, a Novel Transmembrane Iron-Sulfur Flavoprotein Necessary for Nitrous Oxide Respiration

Wunsch

Zumft

2005

J Bacteriol

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“…The nature of NarC as a cytochrome c and its probable stoichiometric synthesis with the NR subunits suggest a role for this protein as a component of the electron transport chain toward the NR. In this sense, the presence of a 16 kDa diheme cytochrome c (NapB) as part of the periplasmic NR from Paracoccus pantotrophus could support such a potential role for NarC [1]. Having in mind that Thermus belongs to one of the oldest evolutionary branches of the bacteria domain, it is tempting to speculate that its NR represents an evolutionary precursor of both membrane and periplasmic respiratory NRs.…”

Section: Discussionmentioning

confidence: 99%

A cytochrome c encoded by the nar operon is required for the synthesis of active respiratory nitrate reductase in Thermus thermophilus

et al. 2002

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A cytochrome c (NarC) is encoded as the ¢rst gene of the operon for nitrate respiration in Thermus thermophilus. NarC is required for anaerobic growth and for the synthesis of active nitrate reductase (NR). The K K and N N subunits (NarG, NarJ) of the NR were constitutively expressed in narC: :kat mutants, but NarG appeared in the soluble fraction instead of associated with the membranes. Our data demonstrate for NarC an essential role in the synthesis of active enzyme and for the attachment to the membrane of the respiratory NR from T. thermophilus. ß 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

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“…One cupredoxin-like domain contains a binuclear copper center known as Cu A . The Cu A center can undergo a one-electron redox change and hence has a function similar to that in the well-known aa 3 -type cytochrome c oxidases (CcO) where it serves to receive an electron from soluble cytochromes c 8 (Fig. 1c).…”

Section: Introductionmentioning

confidence: 99%

Formation of a cytochrome c–nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus

et al. 2005

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Nitrous oxide reductase (N 2 OR) catalyses the final step of bacterial denitrification, the two-electron reduction of nitrous oxide (N 2 O) to dinitrogen (N 2 ). N 2 OR contains two metal centers; a binuclear copper center, Cu A , that serves to receive electrons from soluble donors, and a tetranuclear copper-sulfide center, Cu Z , at the active site. Stopped flow experiments at low ionic strengths reveal rapid electron transfer (k obs = 150 s −1 ) between reduced horse heart (HH) cytochrome c and the Cu A center in fully oxidized N 2 OR. When fully reduced N 2 OR was mixed with oxidized cytochrome c, a similar rate of electron transfer was recorded for the reverse reaction, followed by a much slower internal electron transfer from Cu Z to Cu A (k obs = 0.1-0.4 s −1 ). The internal electron transfer process is likely to represent the rate-determining step in the catalytic cycle. Remarkably, in the absence of cytochrome c, fully reduced N 2 OR is inert towards its substrate, even though sufficient electrons are stored to initiate a single turnover. However, in the presence of reduced cytochrome c and N 2 O, a single turnover occurs after a lag-phase. We propose that a conformational change in N 2 OR is induced by its specific interaction with cytochrome c that in turn either permits electron transfer between Cu A and Cu Z or controls the rate of N 2 O decomposition at the active site.

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Enzymes and associated electron transport systems that catalyse the respiratory reduction of nitrogen oxides and oxyanions

Cited by 567 publications

References 570 publications

Functional Domains of NosR, a Novel Transmembrane Iron-Sulfur Flavoprotein Necessary for Nitrous Oxide Respiration

Functional Domains of NosR, a Novel Transmembrane Iron-Sulfur Flavoprotein Necessary for Nitrous Oxide Respiration

A cytochrome c encoded by the nar operon is required for the synthesis of active respiratory nitrate reductase in Thermus thermophilus

Formation of a cytochrome c–nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus

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