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Publication Abstract from PubMed

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 A, 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.

Dimeric structures of quinol-dependent nitric oxide reductases (qNORs) revealed by cryo-electron microscopy.,Gopalasingam CC, Johnson RM, Chiduza GN, Tosha T, Yamamoto M, Shiro Y, Antonyuk SV, Muench SP, Hasnain SS Sci Adv. 2019 Aug 28;5(8):eaax1803. doi: 10.1126/sciadv.aax1803. eCollection 2019, Aug. PMID:31489376^[1]

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