Journal: Sci Adv / Year: 2023 Title: Investigation of hydrated channels and proton pathways in a high-resolution cryo-EM structure of mammalian complex I. Authors: Daniel N Grba / Injae Chung / Hannah R Bridges / Ahmed-Noor A Agip / Judy Hirst / Abstract: Respiratory complex I, a key enzyme in mammalian metabolism, captures the energy released by reduction of ubiquinone by NADH to drive protons across the inner mitochondrial membrane, generating the ...Respiratory complex I, a key enzyme in mammalian metabolism, captures the energy released by reduction of ubiquinone by NADH to drive protons across the inner mitochondrial membrane, generating the proton-motive force for ATP synthesis. Despite remarkable advances in structural knowledge of this complicated membrane-bound enzyme, its mechanism of catalysis remains controversial. In particular, how ubiquinone reduction is coupled to proton pumping and the pathways and mechanisms of proton translocation are contested. We present a 2.4-Å resolution cryo-EM structure of complex I from mouse heart mitochondria in the closed, active (ready-to-go) resting state, with 2945 water molecules modeled. By analyzing the networks of charged and polar residues and water molecules present, we evaluate candidate pathways for proton transfer through the enzyme, for the chemical protons for ubiquinone reduction, and for the protons transported across the membrane. Last, we compare our data to the predictions of extant mechanistic models, and identify key questions to answer in future work to test them.
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: blot for 10 seconds before plunging.
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Electron microscopy
Microscope
FEI TITAN KRIOS
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / Number grids imaged: 1 / Number real images: 2674 / Average exposure time: 2.53 sec. / Average electron dose: 39.94 e/Å2
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Movie
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Open data
Basic information
Respiratory complex I
Map data
Sample
Keywords
Function and homology information
Authors
United Kingdom, 2 items 
Citation
Structure visualization
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emd_16965.png
http://ftp.pdbj.org/pub/emdb/structures/EMD-16965
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Electron microscopy
