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N<sub>2</sub>O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase

N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase


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POMOWSKI, Anja, Walter G. ZUMFT, Peter M. H. KRONECK, Oliver EINSLE, 2011. N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase. In: Nature. 477(7363), pp. 234-237. ISSN 0028-0836. eISSN 1476-4687

@article{Pomowski2011-08-14bindi-38800, title={N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase}, year={2011}, doi={10.1038/nature10332}, number={7363}, volume={477}, issn={0028-0836}, journal={Nature}, pages={234--237}, author={Pomowski, Anja and Zumft, Walter G. and Kroneck, Peter M. H. and Einsle, Oliver} }

2011-08-14 Pomowski, Anja Kroneck, Peter M. H. Kroneck, Peter M. H. N<sub>2</sub>O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase Zumft, Walter G. 2017-05-09T09:02:46Z Nitrous oxide (N<sub>2</sub>O) is generated by natural and anthropogenic processes and has a critical role in environmental chemistry. It has an ozone-depleting potential similar to that of hydrochlorofluorocarbons as well as a global warming potential exceeding that of CO<sub>2</sub> 300-fold. In bacterial denitrification, N<sub>2</sub>O is reduced to N<sub>2</sub> by the copper-dependent nitrous oxide reductase (N<sub>2</sub>OR). This enzyme carries the mixed-valent Cu(A) centre and the unique, tetranuclear Cu<sub>Z</sub> site. Previous structural data were obtained with enzyme isolated in the presence of air that is catalytically inactive without prior reduction. Its Cu<sub>Z</sub> site was described as a [4Cu:S] centre, and the substrate-binding mode and reduction mechanism remained elusive. Here we report the structure of purple N<sub>2</sub>OR from Pseudomonas stutzeri, handled under the exclusion of dioxygen, and locate the substrate in N<sub>2</sub>O-pressurized crystals. The active Cu<sub>Z</sub> cluster contains two sulphur atoms, yielding a [4Cu:2S] stoichiometry; and N<sub>2</sub>O bound side-on at Cu<sub>Z</sub>, in close proximity to Cu<sub>A</sub>. With the substrate located between the two clusters, electrons are transferred directly from Cu<sub>A</sub> to N<sub>2</sub>O, which is activated by side-on binding in a specific binding pocket on the face of the [4Cu:2S] centre. These results reconcile a multitude of available biochemical data on N<sub>2</sub>OR that could not be explained by earlier structures, and outline a mechanistic pathway in which both metal centres and the intervening protein act in concert to achieve catalysis. This structure represents the first direct observation, to our knowledge, of N<sub>2</sub>O bound to its reductase, and sheds light on the functionality of metalloenzymes that activate inert small-molecule substrates. The principle of using distinct clusters for substrate activation and for reduction may be relevant for similar systems, in particular nitrogen-fixing nitrogenase. Einsle, Oliver Pomowski, Anja eng Einsle, Oliver Zumft, Walter G. 2017-05-09T09:02:46Z

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