N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase
14.08.2011
Pomowski A, Zumft WG, Kroneck PMH, Einsle O
Nature 2011; 477(7363):234-7
Nitrous oxide reductase (N2OR) is a copper-containing protein with two unique metal sites, the dinuclear CuA, a presumed electron transfer center, and the tetranuclear CuZ, the actual active site. We have determined the first crystal structure of the physiologically active, purple form of N2OR from Pseudomonas stutzeri, and we were able to show the binding mode of N2O on the CuZ cluster.
Unexpectedly, the substrate bound in a position between the CuA and CuZ site, tightly held in place by the protein. Electron transfer likely occurs directly from CuA to N2O, so that the actual ‘active site’ is the entire complex arrangement of two metal centers and the protein matrix. The structure marks the first direct observation of the binding mode of a highly unsaturated nitrogen compound in a metalloenzyme and will provide essential clues for understanding the catalytic mechanism of N2OR.
