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

Authors :
Takehiko Tosha
C.C. Gopalasingam
S. Samar Hasnain
George N. Chiduza
Stephen P. Muench
Yoshitsugu Shiro
Masaki Yamamoto
Rachel M. Johnson
Svetlana V. Antonyuk
Source :
Science Advances
Publication Year :
2019

Abstract

qNORs that catalyze the reduction of nitric oxide to nitrous oxide are dimeric and obtain their protons from cytoplasmic end.<br />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.

Details

Language :
English
ISSN :
23752548
Database :
OpenAIRE
Journal :
Science Advances
Accession number :
edsair.doi.dedup.....5e3a2b48a51a78cac3cba6fcc50a607d