Crystal structure of quinol-dependent nitric oxide reductase from Geobacillus stearothermophilus

Introduction

This blog aims to present findings on crystal structure of nitric oxide reductase (NOR) from Geobacillus strearothermophilus by Yushi Matsumoto et al. 

NOR is an evolutionarily conserved anaerobic respiration enzyme involved in microbial denitrification process. NOR catalyzes the reduction of nitric oxide NO to nitrous oxide N₂O:NO₃⁻ → NO₂⁻ → NO → N₂O → N_2,  both of which are potent greenhouse gases. It has been identified that NOR share sequence similarities with its close relative cytochrome oxidase(COX), an enzyme that catalyzes the reduction of O₂ to water in aerobic respiration. NOR can be divided into two subgroups consisting of distinct combinations of subunits and cofactors: cNOR, composed of NorC and NorB subunits; and qNOR. 

In their previous study on cNOR, it was found that certain similarities exist between NOR and COX , for example both contain metal ligands and belong to heme copper oxidase family. But they differ in more detailed structure such as the coordination geometry of binuclear center. However, little is known about the structure-function relationship of qNOR and this paper attempts to fill the blank by comparing structures of COX, qNOR and cNOR, with discussions on their functional conversions. 

Geobacillus strearothermophilus (1)