7aqa | pdb_00007aqa
Pseudomonas stutzeri nitrous oxide reductase mutant, H382A
Structural highlights
FunctionNOSZ_STUST Nitrous-oxide reductase is part of a bacterial respiratory system which is activated under anaerobic conditions in the presence of nitrate or nitrous oxide.[1] Publication Abstract from PubMedNitrous oxide reductase (N2OR) is the only known enzyme reducing environmentally critical nitrous oxide (N2O) to dinitrogen (N2) as the final step of bacterial denitrification. The assembly process of its unique catalytic [4Cu:2S] cluster CuZ remains scarcely understood. Here we report on a mutagenesis study of all seven histidine ligands coordinating this copper center, followed by spectroscopic and structural characterization and based on an established, functional expression system for Pseudomonas stutzeri N2OR in Escherichia coli. While no copper ion was found in the CuZ binding site of variants H129A, H130A, H178A, H326A, H433A and H494A, the H382A variant carried a catalytically inactive [3Cu:2S] center, in which one sulfur ligand, SZ2, had relocated to form a weak hydrogen bond to the sidechain of the nearby lysine residue K454. This link provides sufficient stability to avoid the loss of the sulfide anion. The UV-vis spectra of this cluster are strikingly similar to those of the active enzyme, implying that the flexibility of SZ2 may have been observed before, but not recognized. The sulfide shift changes the metal coordination in CuZ and is thus of high mechanistic interest. A [3Cu:2S] cluster provides insight into the assembly and function of the CuZ site of nitrous oxide reductase.,Zhang L, Bill E, Kroneck PMH, Einsle O Chem Sci. 2021 Jan 15;12(9):3239-3244. doi: 10.1039/d0sc05204c. PMID:34164092[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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