Journal: Nat Commun / Year: 2026 Title: Post-catalysis structures of mitochondrial complex I with ubiquinol-10 bound in the active site. Authors: Injae Chung / Caroline S Pereira / John J Wright / Guilherme M Arantes / Judy Hirst / Abstract: Respiratory complex I is a multi-subunit energy-transducing membrane enzyme essential for mitochondrial and cellular energy metabolism. It couples NADH oxidation and ubiquinone-10 (Q) reduction to ...Respiratory complex I is a multi-subunit energy-transducing membrane enzyme essential for mitochondrial and cellular energy metabolism. It couples NADH oxidation and ubiquinone-10 (Q) reduction to the concomitant pumping of four protons to generate the proton-motive force that powers oxidative phosphorylation. Despite recent advances in structural knowledge of complex I, many mechanistic aspects including the reactive binding poses of Q, how Q reduction initiates the proton transfer cascade, and how protons move through the membrane domain, remain unclear. Here, we use electron cryomicroscopy to determine structures of mammalian complex I, reconstituted into phospholipid nanodiscs containing exogenous Q and reduced by NADH, to global resolutions of 2.0 to 2.6 Å. Two conformations of a reduced QH molecule are observed, fully inserted into the Q-binding channel in the turnover-relevant closed state. By comparing the quinone species bound in oxidised and reduced complex I structures, paired with molecular dynamics simulations to investigate the charge states of key surrounding residues, we propose a series of substrate binding poses that Q transits through for reduction. Our highly hydrated structures exhibit near-continuous proton-transfer connections along the length of the membrane domain, enabling comparisons between them to assist in identifying the proton-transfer control points that are essential to catalysis.
UniProtKB: NADH dehydrogenase [ubiquinone] iron-sulfur protein 3, mitochondrial
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Macromolecule #4: NADH dehydrogenase [ubiquinone] iron-sulfur protein 2, mitochondrial
Macromolecule
Name: NADH dehydrogenase [ubiquinone] iron-sulfur protein 2, mitochondrial type: protein_or_peptide / ID: 4 Details: Harbours a naturally occurring mutation Q129R (Q162R) in the Cambridge UK population Number of copies: 1 / Enantiomer: LEVO / EC number: NADH:ubiquinone reductase (H+-translocating)
Model: UltrAuFoil / Material: GOLD / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 90 sec. Details: Following glow discharge for 90 s at 20 mA, the grid was treated for 48 hours in an anaerobic glovebox in ethanol containing 5 mM 11-mercaptoundecyl hexaethyleneglycol, washed three times in ...Details: Following glow discharge for 90 s at 20 mA, the grid was treated for 48 hours in an anaerobic glovebox in ethanol containing 5 mM 11-mercaptoundecyl hexaethyleneglycol, washed three times in ethanol and dried prior to blotting
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV Details: Mix with NADH, then blot for 10 seconds before plunging.
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Electron microscopy
Microscope
TFS KRIOS
Specialist optics
Energy filter - Slit width: 20 eV
Details
AutoStigmate and AutoComa on EPU, no AutoCTF
Image recording
Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / Number grids imaged: 1 / Number real images: 13056 / Average exposure time: 2.14 sec. / Average electron dose: 40.29 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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Function and homology information
Bos taurus (domestic cattle)
Authors
United Kingdom, 3 items 
Citation
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emd_55033.png
http://ftp.pdbj.org/pub/emdb/structures/EMD-55033
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Electron microscopy
FIELD EMISSION GUN
