Work

Visualizing the mechanism of quinol oxidation and inhibition of a bd -type oxidase using cryo-EM

Year: 2026

Type: article

Abstract: Cytochrome bd is a prokaryotic terminal oxidase recognized as an antibiotic target against various pathogens. Despite its critical role in respiration, failure to capture the mechanism of quinol oxidation and inhibition prohibits structure guided drug discovery. Here, we present cryo–electron microscopy structures of Escherichia coli cytochrome bd -I in monomeric and dimeric forms, in several quinone and inhibitor-bound states. We identify a dynamic Q-loop lid that undergoes a disorder-to-order transition upon substrate binding to the dimer, completing the active site and enabling catalysis. Structure-guided mutagenesis confirms Tyr243 CydA and Arg298 CydA as conserved catalytic residues only found in long Q-loop oxidases, highlighting evolutionary divergence from other subfamilies. Inhibition by Aurachin D triggers refolding of the active site, occluding substrate access via an Asp239 CydA -mediated mechanism. The structural and mechanistic insights presented here establish a comprehensive framework, opening paths for drug discovery against bd oxidases.

Source: Science Advances

DOI: 10.1126/sciadv.aec9946

Authors: Tijn T. van der Velden, Kanwal Kayastha, Famke Pelser, Steffen Brünle, Lars J. C. Jeuken

Institution: Leiden University

Language: English

Topic: Enzyme Structure and Function

Subfield: Structural Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: gold

Estimated APC paid: $4,500

Funders: Universiteit Leiden, Nederlandse Organisatie voor Wetenschappelijk Onderzoek