Redox-dependent Open and Closed Forms of the Active Site of the Bacterial Respiratory Nitric-oxide Reductase Revealed by Cyanide Binding Studies

The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe–non-heme Fe] active site rather than the [heme Fe–CuB] active site normall...

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Bibliographic Details
Published in:The Journal of biological chemistry 2004-04, Vol.279 (17), p.17120-17125
Main Authors: Grönberg, Karin L.C., Watmough, Nicholas J., Thomson, Andrew J., Richardson, David J., Field, Sarah J.
Format: Article
Language:English
Subjects:
Bacteria - enzymology
Binding Sites
Catalysis
Cyanides - chemistry
Dose-Response Relationship, Drug
Electrons
Heme - chemistry
Iron
Kinetics
Ligands
Nitric Oxide - metabolism
Oxidation-Reduction
Oxidoreductases - chemistry
Oxygen - metabolism
Oxygen Consumption
Paracoccus denitrificans
Paracoccus denitrificans - enzymology
Potassium Cyanide - chemistry
Potassium Cyanide - pharmacology
Protein Binding
Time Factors
Ultraviolet Rays
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Summary:The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe–non-heme Fe] active site rather than the [heme Fe–CuB] active site normally associated with oxygen reduction. Paracoccus denitrificans NOR is spectrally characterized by a ligand-to-metal charge transfer absorption band at 595 nm, which arises from the high spin ferric heme iron of a μ-oxo-bridged [heme Fe(III)–O–Fe(III)] active site. On reduction of the nonheme iron, the μ-oxo bridge is broken, and the ferric heme iron is hydroxylated or hydrated, depending on the pH. At present, the catalytic cycle of NOR is a matter of much debate, and it is not known to which redox state(s) of the enzyme nitric oxide can bind. This study has used cyanide to probe the nature of the active site in a number of different redox states. Our observations suggest that the μ-oxo-bridged [heme Fe(III)–O–Fe(III)] active site represents a closed or resting state of NOR that can be opened by reduction of the non-heme iron.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M400824200