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The Long-Range High-pH Proton Channel Facilitates the Nitrite Reduction in Copper-Containing Nitrite Reductase

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Copper-containing nitrite reductase (CuNiR) catalyzes the conversion of nitrite (NO 2 – ) to nitric oxide (NO), requiring sequential proton delivery through long-range high-pH and primary proton channels. But the proton transfer (PT) and electron transfer (ET) mechanisms during the critical second protonation remain unclear. Here, we investigate these bioenergetic mechanisms using a two-layer ONIOM approach. Results reveal distinct pathways: the high-pH channel features a water-mediated three-stage PT from Glu113 to W S3, followed by direct PT to Asp98 and proton-coupled β-ET to nitrous acid (HNO 2 ). In contrast, the primary channel proceeds via water-mediated three-stage PTs from Lys128 to His255 and then a water-mediated two-stage proton-coupled β-ET to HNO 2 . Comparative energy analysis shows that the second protonation of NO 2 – is the overall rate-limiting step with the long-range high-pH channel serving as the preferred pathway in CuNiR catalysis. These fundamental mechanisms of CuNiR deepen our understanding of the biological denitrification.

Source: ACS Omega

DOI: 10.1021/acsomega.5c06351

Authors: Xin Qin, Li Li, Qiulan Zhou, Xiaohua Chen

Institutions: Changsha Medical University, Hunan University of Medicine, Chongqing University

Language: English

Topic: Metal-Catalyzed Oxygenation Mechanisms

Subfield: Inorganic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,935