Abstract
Nitrous-oxide reductases (N2OR) catalyze the two-electron reduction of N(2)O to N(2). The crystal structure of N2ORs from Pseudomonas nautica (Pn) and Paracoccus denitrificans (Pd) were solved at resolutions of 2.4 and 1.6 A, respectively. The Pn N2OR structure revealed that the catalytic CuZ center belongs to a new type of metal cluster in which four copper ions are liganded by seven histidine residues. A bridging oxygen moiety and two other hydroxide ligands were proposed to complete the ligation scheme (Brown, K., Tegoni, M., Prudencio, M., Pereira, A. S., Besson, S., Moura, J. J. G., Moura, I., and Cambillau, C. (2000) Nat. Struct. Biol. 7, 191-195). However, in the CuZ cluster, inorganic sulfur chemical determination and the high resolution structure of Pd N2OR identified a bridging inorganic sulfur instead of an oxygen. This result reconciles the novel CuZ cluster with the hitherto puzzling spectroscopic data.
Highlights
Nitrous-oxide reductases (N2OR) catalyze the twoelectron reduction of N2O to N2
The Pseudomonas nautica (Pn) N2O reductase (N2OR) structure revealed that the catalytic CuZ center belongs to a new type of metal cluster in which four copper ions are liganded by seven histidine residues
Inorganic Sulfur Determination—Copper and sulfur were determined for the Pn N2OR in three different samples
Summary
The Pn N2OR structure revealed that the catalytic CuZ center belongs to a new type of metal cluster in which four copper ions are liganded by seven histidine residues. In the CuZ cluster, inorganic sulfur chemical determination and the high resolution structure of Pd N2OR identified a bridging inorganic sulfur instead of an oxygen. This result reconciles the novel CuZ cluster with the hitherto puzzling spectroscopic data. The bridging ligand has recently been proposed to be an inorganic sulfur ion [7], which would reconcile the previous spectroscopic interpretations with the novel CuZ cluster structure. These studies, reported here, confirm the presence of a bridging sulfur in the CuZ cluster
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