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Publication Abstract from PubMed

Copper-containing nitrite reductase (CuNIR) catalyzes the reduction of nitrite (NO(-)2) to nitric oxide (NO) during denitrification. We determined the crystal structures of CuNIR from thermophilic gram-positive bacterium, Geobacillus thermodenitrificans (GtNIR) in chloride- and formate-bound forms of wild type at 1.15 A resolution and the nitrite-bound form of the C135A mutant at 1.90 A resolution. The structure of C135A with nitrite displays a unique eta(1)-O coordination mode of nitrite at the catalytic copper site (T2Cu), which has never been observed at the T2Cu site in known wild-type CuNIRs, because the mobility of two residues essential to catalytic activity, Asp98 and His244, are sterically restricted in GtNIR by Phe109 on a characteristic loop structure that is found above Asp98 and by an unusually short CH-O hydrogen bond observed between His244 and water, respectively. A detailed comparison of the WT structure with the nitrite-bound C135A structure implies the replacement of hydrogen-bond networks around His244 and predicts the flow path of protons consumed by nitrite reduction. On the basis of these observations, the reaction mechanism of GtNIR through the eta(1)-O coordination manner is proposed.

Structural insights into the function of a thermostable copper-containing nitrite reductase.,Fukuda Y, Tse KM, Lintuluoto M, Fukunishi Y, Mizohata E, Matsumura H, Takami H, Nojiri M, Inoue T J Biochem. 2014 Feb;155(2):123-35. doi: 10.1093/jb/mvt107. Epub 2013 Nov 30. PMID:24293549^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.