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Dimeric structures of quinol-dependent nitric oxide reductases (qNORs) revealed by cryo–electron microscopy

DOI: 10.1126/sciadv.aax1803 DOI Help

Authors: Chai C. Gopalasingam (University of Liverpool) , Rachel M. Johnson (University of Leeds) , George N. Chiduza (University of Liverpool) , Takehiko Tosha (RIKEN SPring-8 Center) , Masaki Yamamoto (RIKEN SPring-8 Center) , Yoshitsugu Shiro (University of Hyogo) , Svetlana V. Antonyuk (University of Liverpool) , Stephen P. Muench (University of Leeds) , S. Samar Hasnain (University of Liverpool)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Advances , VOL 5

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 19832

Open Access Open Access

Abstract: Quinol-dependent nitric oxide reductases (qNORs) are membrane-integrated, iron-containing enzymes of the denitrification pathway, which catalyze the reduction of nitric oxide (NO) to the major ozone destroying gas nitrous oxide (N2O). Cryo–electron microscopy structures of active qNOR from Alcaligenes xylosoxidans and an activity-enhancing mutant have been determined to be at local resolutions of 3.7 and 3.2 Å, respectively. They unexpectedly reveal a dimeric conformation (also confirmed for qNOR from Neisseria meningitidis) and define the active-site configuration, with a clear water channel from the cytoplasm. Structure-based mutagenesis has identified key residues involved in proton transport and substrate delivery to the active site of qNORs. The proton supply direction differs from cytochrome c–dependent NOR (cNOR), where water molecules from the cytoplasm serve as a proton source similar to those from cytochrome c oxidase.

Journal Keywords: climate change; greenhouse gas

Subject Areas: Biology and Bio-materials

Diamond Offline Facilities: Electron Bio-Imaging Centre (eBIC)
Instruments: Krios II-Titan Krios II at Diamond

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eaax1803.full.pdf