scholarly journals Functional basis of electron transport within photosynthetic complex I

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Katherine H. Richardson ◽  
John J. Wright ◽  
Mantas Šimėnas ◽  
Jacqueline Thiemann ◽  
Ana M. Esteves ◽  
...  
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Proton Pumping ◽  
Reduction Potentials ◽  
Large Size ◽  
Complex Functions ◽  
High Lability ◽  
Respiratory Complex I ◽  
Double Electron Electron Resonance ◽  
Insight Into

AbstractPhotosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme – the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI (N0, N1 and N2), and unambiguously assign them to the structure using double electron-electron resonance. We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.

scholarly journals Functional basis of electron transport within photosynthetic complex I

2021 ◽  
Author(s):  
Katherine H. Richardson ◽  
John J. Wright ◽  
Mantas Šimėnas ◽  
Jacqueline Thiemann ◽  
Ana M. Esteves ◽  
...  
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Cell Types ◽  
Proton Pumping ◽  
Higher Plant ◽  
Reduction Potentials ◽  
Large Size ◽  
Complex Functions ◽  
High Lability ◽  
Double Electron Electron Resonance

AbstractPhotosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes, and is fundamental to bioenergetics in photosynthetic bacteria and some higher plant cell types. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme – the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI, and unambiguously assign them to the structure using double electron-electron resonance (DEER). We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.

scholarly journals Susceptibility of the Formate Hydrogenlyase Reaction to the Protonophore CCCP Depends on the Total Hydrogenase Composition

Inorganics ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 38
Author(s):  
Janik Telleria Marloth ◽  
Constanze Pinske
Keyword(s):  
Complex I ◽  
H2 Production ◽  
Proton Pumping ◽  
Fermentative Hydrogen Production ◽  
Iron Sulfur ◽  
Formate Hydrogenlyase ◽  
Respiratory Complex I ◽  
Fermentative Hydrogen ◽  
Pumping Activity ◽  
Higher Sensitivity

Fermentative hydrogen production by enterobacteria derives from the activity of the formate hydrogenlyase (FHL) complex, which couples formate oxidation to H2 production. The molybdenum-containing formate dehydrogenase and type-4 [NiFe]-hydrogenase together with three iron-sulfur proteins form the soluble domain, which is attached to the membrane by two integral membrane subunits. The FHL complex is phylogenetically related to respiratory complex I, and it is suspected that it has a role in energy conservation similar to the proton-pumping activity of complex I. We monitored the H2-producing activity of FHL in the presence of different concentrations of the protonophore CCCP. We found an inhibition with an apparent EC50 of 31 µM CCCP in the presence of glucose, a higher tolerance towards CCCP when only the oxidizing hydrogenase Hyd-1 was present, but a higher sensitivity when only Hyd-2 was present. The presence of 200 mM monovalent cations reduced the FHL activity by more than 20%. The Na+/H+ antiporter inhibitor 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) combined with CCCP completely inhibited H2 production. These results indicate a coupling not only between Na+ transport activity and H2 production activity, but also between the FHL reaction, proton import and cation export.

scholarly journals Functional Water Wires Catalyze Long-Range Proton Pumping in the Mammalian Respiratory Complex I

2020 ◽  
Vol 142 (52) ◽  
pp. 21758-21766
Author(s):  
Michael Röpke ◽  
Patricia Saura ◽  
Daniel Riepl ◽  
Maximilian C. Pöverlein ◽  
Ville R. I. Kaila
Keyword(s):  
Long Range ◽  
Complex I ◽  
Proton Pumping ◽  
Respiratory Complex ◽  
Respiratory Complex I

The coupling mechanism of mammalian respiratory complex I

Science ◽  
2020 ◽  
Vol 370 (6516) ◽  
pp. eabc4209 ◽  
Author(s):  
Domen Kampjut ◽  
Leonid A. Sazanov
Keyword(s):  
Conformational Changes ◽  
Complex I ◽  
Electrostatic Interactions ◽  
Proton Translocation ◽  
Proton Pumping ◽  
State Transitions ◽  
Coupling Mechanism ◽  
Cryo Electron Microscopy ◽  
Open Conformation ◽  
Respiratory Complex I

Mitochondrial complex I couples NADH:ubiquinone oxidoreduction to proton pumping by an unknown mechanism. Here, we present cryo–electron microscopy structures of ovine complex I in five different conditions, including turnover, at resolutions up to 2.3 to 2.5 angstroms. Resolved water molecules allowed us to experimentally define the proton translocation pathways. Quinone binds at three positions along the quinone cavity, as does the inhibitor rotenone that also binds within subunit ND4. Dramatic conformational changes around the quinone cavity couple the redox reaction to proton translocation during open-to-closed state transitions of the enzyme. In the induced deactive state, the open conformation is arrested by the ND6 subunit. We propose a detailed molecular coupling mechanism of complex I, which is an unexpected combination of conformational changes and electrostatic interactions.

Mammalian Respiratory Complex I Through the Lens of Cryo-EM

2019 ◽  
Vol 48 (1) ◽  
pp. 165-184 ◽  
Author(s):  
Ahmed-Noor A. Agip ◽  
James N. Blaza ◽  
Justin G. Fedor ◽  
Judy Hirst
Keyword(s):  
Complex I ◽  
Catalytic Mechanism ◽  
Structural Data ◽  
Proton Pumping ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Respiratory Complex ◽  
Data Collection Strategy ◽  
Structural Work ◽  
Membrane Bound ◽  
Respiratory Complex I

Single-particle electron cryomicroscopy (cryo-EM) has led to a revolution in structural work on mammalian respiratory complex I. Complex I (mitochondrial NADH:ubiquinone oxidoreductase), a membrane-bound redox-driven proton pump, is one of the largest and most complicated enzymes in the mammalian cell. Rapid progress, following the first 5-Å resolution data on bovine complex I in 2014, has led to a model for mouse complex I at 3.3-Å resolution that contains 96% of the 8,518 residues and to the identification of different particle classes, some of which are assigned to biochemically defined states. Factors that helped improve resolution, including improvements to biochemistry, cryo-EM grid preparation, data collection strategy, and image processing, are discussed. Together with recent structural data from an ancient relative, membrane-bound hydrogenase, cryo-EM on mammalian complex I has provided new insights into the proton-pumping machinery and a foundation for understanding the enzyme's catalytic mechanism.

scholarly journals Cryo-EM structure of respiratory complex I at work

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Kristian Parey ◽  
Ulrich Brandt ◽  
Hao Xie ◽  
Deryck J Mills ◽  
Karin Siegmund ◽  
...  
Keyword(s):  
Complex I ◽  
Atp Synthesis ◽  
Proton Pumping ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Membrane Protein Complex ◽  
Change Mechanism ◽  
Steady State Activity ◽  
Respiratory Complex I ◽  
Ubiquinone Binding

Mitochondrial complex I has a key role in cellular energy metabolism, generating a major portion of the proton motive force that drives aerobic ATP synthesis. The hydrophilic arm of the L-shaped ~1 MDa membrane protein complex transfers electrons from NADH to ubiquinone, providing the energy to drive proton pumping at distant sites in the membrane arm. The critical steps of energy conversion are associated with the redox chemistry of ubiquinone. We report the cryo-EM structure of complete mitochondrial complex I from the aerobic yeast Yarrowia lipolytica both in the deactive form and after capturing the enzyme during steady-state activity. The site of ubiquinone binding observed during turnover supports a two-state stabilization change mechanism for complex I.

scholarly journals Deactivation blocks proton pathways in the mitochondrial complex I

2021 ◽  
Vol 118 (29) ◽  
pp. e2019498118
Author(s):  
Michael Röpke ◽  
Daniel Riepl ◽  
Patricia Saura ◽  
Andrea Di Luca ◽  
Max E. Mühlbauer ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Conformational Changes ◽  
Complex I ◽  
Large Scale ◽  
Proton Pumping ◽  
Cellular Respiration ◽  
Transmembrane Helices ◽  
Membrane Bound ◽  
Respiratory Complex I ◽  
Microscopy Data

Cellular respiration is powered by membrane-bound redox enzymes that convert chemical energy into an electrochemical proton gradient and drive the energy metabolism. By combining large-scale classical and quantum mechanical simulations with cryo-electron microscopy data, we resolve here molecular details of conformational changes linked to proton pumping in the mammalian complex I. Our data suggest that complex I deactivation blocks water-mediated proton transfer between a membrane-bound quinone site and proton-pumping modules, decoupling the energy-transduction machinery. We identify a putative gating region at the interface between membrane domain subunits ND1 and ND3/ND4L/ND6 that modulates the proton transfer by conformational changes in transmembrane helices and bulky residues. The region is perturbed by mutations linked to human mitochondrial disorders and is suggested to also undergo conformational changes during catalysis of simpler complex I variants that lack the “active”-to-“deactive” transition. Our findings suggest that conformational changes in transmembrane helices modulate the proton transfer dynamics by wetting/dewetting transitions and provide important functional insight into the mammalian respiratory complex I.

scholarly journals The proton-pumping respiratory complex I of bacteria and mitochondria and its homologue in chloroplasts

FEBS Letters ◽  
1995 ◽  
Vol 367 (2) ◽  
pp. 107-111 ◽  
Author(s):  
Thorsten Friedrich ◽  
Klaus Steinmüller ◽  
Hanns Weiss
Keyword(s):  
Complex I ◽  
Proton Pumping ◽  
Respiratory Complex ◽  
Respiratory Complex I
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