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 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 The Higher Plant Plastid Complex I (NDH) is a Reversible Proton Pump that increases ATP production by Cyclic Electron Flow Around Photosystem I

2016 ◽  
Author(s):  
Deserah D. Strand ◽  
Nicholas Fisher ◽  
David M. Kramer
Keyword(s):  
Electron Transfer ◽  
Photosystem I ◽  
Complex I ◽  
Electron Flow ◽  
Proton Pumping ◽  
Cyclic Electron Flow ◽  
Higher Plant ◽  
Atp Production ◽  
Respiratory Complex I ◽  
Chloroplast Stroma

AbstractCyclic electron flow around photosystem I (CEF) is critical for balancing the photosynthetic energy budget of the chloroplast, by generating ATP without net production of NADPH. We demonstrate that the chloroplast NADPH dehydrogenase complex (NDH), a homolog to respiratory Complex I, pumps approximately two protons from the chloroplast stroma to the lumen per electron transferred from ferredoxin to plastoquinone, effectively increasing the efficiency of ATP production via CEF by two-fold compared to CEF pathways involving non-proton-pumping plastoquinone reductases. Under certain physiological conditions, the coupling of proton and electron transfer reactions within NDH should enable a non-canonical mode of photosynthetic electron transfer, allowing electron transfer from plastoquinol to NADPH to be driven by the thylakoid proton motive force possibly helping to sense or remediate mismatches in the photosynthetic budget.

scholarly journals Overexpression of the Rieske FeS protein of the Cytochromeb6fcomplex increases C4photosynthesis

2019 ◽  
Author(s):  
Maria Ermakova ◽  
Patricia E. Lopez-Calcagno ◽  
Christine A. Raines ◽  
Robert T. Furbank ◽  
Susanne von Caemmerer
Keyword(s):  
Electron Transport ◽  
Cell Types ◽  
Bundle Sheath ◽  
Assimilation Rate ◽  
Higher Plant ◽  
Bundle Sheath Cells ◽  
Electron Transport Chains ◽  
Photosynthetic Complexes ◽  
Rieske Fes Protein ◽  
Sheath Cells

AbstractC4plants contribute 20% to the global primary productivity despite representing only 4% of higher plant species. Their CO2concentrating mechanism operating between mesophyll and bundle sheath cells increases CO2partial pressure at the site of Rubisco and hence photosynthetic efficiency. Electron transport chains in both cell types supply ATP and NADPH for C4photosynthesis. Since Cytochromeb6fis a key point of control of electron transport in C3plants, we constitutively overexpressed the Rieske FeS subunit inSetaria viridisto study the effects on C4photosynthesis. Rieske FeS overexpression resulted in a higher content of Cytochromeb6fin both mesophyll and bundle sheath cells without marked changes in abundances of other photosynthetic complexes and Rubisco. Plants with higher Cytochromeb6fabundance showed better light conversion efficiency in both Photosystems and could generate higher proton-motive force across the thylakoid membrane. Rieske FeS abundance correlated with CO2assimilation rate and plants with a 10% increase in Rieske FeS content showed a 10% increase in CO2assimilation rate at ambient and saturating CO2and high light. Our results demonstrate that Cytochromeb6fcontrols the rate of electron transport in C4plants and that removing electron transport limitations can increase the rate of C4photosynthesis.

scholarly journals Paracoccus denitrificans: a genetically tractable model system for studying respiratory complex I

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen D. Jarman ◽  
Olivier Biner ◽  
John J. Wright ◽  
Judy Hirst
Keyword(s):  
Complex I ◽  
Paracoccus Denitrificans ◽  
Model System ◽  
Proton Pumping ◽  
Model Systems ◽  
Metabolic Enzyme ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Inner Mitochondrial Membrane

AbstractMitochondrial complex I (NADH:ubiquinone oxidoreductase) is a crucial metabolic enzyme that couples the free energy released from NADH oxidation and ubiquinone reduction to the translocation of four protons across the inner mitochondrial membrane, creating the proton motive force for ATP synthesis. The mechanism by which the energy is captured, and the mechanism and pathways of proton pumping, remain elusive despite recent advances in structural knowledge. Progress has been limited by a lack of model systems able to combine functional and structural analyses with targeted mutagenic interrogation throughout the entire complex. Here, we develop and present the α-proteobacterium Paracoccus denitrificans as a suitable bacterial model system for mitochondrial complex I. First, we develop a robust purification protocol to isolate highly active complex I by introducing a His6-tag on the Nqo5 subunit. Then, we optimize the reconstitution of the enzyme into liposomes, demonstrating its proton pumping activity. Finally, we develop a strain of P. denitrificans that is amenable to complex I mutagenesis and create a catalytically inactive variant of the enzyme. Our model provides new opportunities to disentangle the mechanism of complex I by combining mutagenesis in every subunit with established interrogative biophysical measurements on both the soluble and membrane bound enzymes.

scholarly journals A Genome-Scale Metabolic Model of Anabaena 33047 to Guide Genetic Modifications to Overproduce Nylon Monomers

Metabolites ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 168
Author(s):  
John I. Hendry ◽  
Hoang V. Dinh ◽  
Debolina Sarkar ◽  
Lin Wang ◽  
Anindita Bandyopadhyay ◽  
...  
Keyword(s):  
Electron Transport ◽  
Pyruvate Decarboxylase ◽  
Metabolic Model ◽  
Cell Types ◽  
Economic Feasibility ◽  
Nitrogen Fixing ◽  
Design Algorithm ◽  
A Genome ◽  
Anabaena Sp ◽  
Genome Scale

Nitrogen fixing-cyanobacteria can significantly improve the economic feasibility of cyanobacterial production processes by eliminating the requirement for reduced nitrogen. Anabaena sp. ATCC 33047 is a marine, heterocyst forming, nitrogen fixing cyanobacteria with a very short doubling time of 3.8 h. We developed a comprehensive genome-scale metabolic (GSM) model, iAnC892, for this organism using annotations and content obtained from multiple databases. iAnC892 describes both the vegetative and heterocyst cell types found in the filaments of Anabaena sp. ATCC 33047. iAnC892 includes 953 unique reactions and accounts for the annotation of 892 genes. Comparison of iAnC892 reaction content with the GSM of Anabaena sp. PCC 7120 revealed that there are 109 reactions including uptake hydrogenase, pyruvate decarboxylase, and pyruvate-formate lyase unique to iAnC892. iAnC892 enabled the analysis of energy production pathways in the heterocyst by allowing the cell specific deactivation of light dependent electron transport chain and glucose-6-phosphate metabolizing pathways. The analysis revealed the importance of light dependent electron transport in generating ATP and NADPH at the required ratio for optimal N2 fixation. When used alongside the strain design algorithm, OptForce, iAnC892 recapitulated several of the experimentally successful genetic intervention strategies that over produced valerolactam and caprolactam precursors.

scholarly journals Cardiolipin promotes electron transport between ubiquinone and complex I to rescue PINK1 deficiency

2017 ◽  
Vol 216 (3) ◽  
pp. 695-708 ◽  
Author(s):  
Melissa Vos ◽  
Ann Geens ◽  
Claudia Böhm ◽  
Liesbeth Deaulmerie ◽  
Jef Swerts ◽  
...  
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Fatty Acid Synthase ◽  
Induced Pluripotent Stem Cell ◽  
Mitochondrial Inner Membrane ◽  
Mitochondrial Defects ◽  
Mouse Cells ◽  
Induced Pluripotent ◽  
Specific Lipid ◽  
Pharmacologic Inhibition

PINK1 is mutated in Parkinson’s disease (PD), and mutations cause mitochondrial defects that include inefficient electron transport between complex I and ubiquinone. Neurodegeneration is also connected to changes in lipid homeostasis, but how these are related to PINK1-induced mitochondrial dysfunction is unknown. Based on an unbiased genetic screen, we found that partial genetic and pharmacological inhibition of fatty acid synthase (FASN) suppresses toxicity induced by PINK1 deficiency in flies, mouse cells, patient-derived fibroblasts, and induced pluripotent stem cell–derived dopaminergic neurons. Lower FASN activity in PINK1 mutants decreases palmitate levels and increases the levels of cardiolipin (CL), a mitochondrial inner membrane–specific lipid. Direct supplementation of CL to isolated mitochondria not only rescues the PINK1-induced complex I defects but also rescues the inefficient electron transfer between complex I and ubiquinone in specific mutants. Our data indicate that genetic or pharmacologic inhibition of FASN to increase CL levels bypasses the enzymatic defects at complex I in a PD model.

Electron transport pathways for the oxidation of endogenous substrate(s) in Acidithiobacillus ferrooxidans

2006 ◽  
Vol 52 (4) ◽  
pp. 317-327 ◽  
Author(s):  
Yongqiang Chen ◽  
Isamu Suzuki
Keyword(s):  
Electron Transport ◽  
Electron Acceptor ◽  
Acidithiobacillus Ferrooxidans ◽  
Complex I ◽  
Iron Chelators ◽  
Endogenous Respiration ◽  
Sugar Alcohols ◽  
Transport Pathways ◽  
Endogenous Substrate ◽  
Transport Inhibitors

Oxidation of endogenous substrate(s) of Acidithiobacillus ferrooxidans with O2 or Fe3+ as electron acceptor was studied in the presence of uncouplers and electron transport inhibitors. Endogenous substrate was oxidized with a respiratory quotient (CO2 produced/O2 consumed) of 1.0, indicating its carbohydrate nature. The oxidation was inhibited by complex I inhibitors (rotenone, amytal, and piericidin A) only partially, but piericidin A inhibited the oxidation with Fe3+ nearly completely. The oxidation was stimulated by uncouplers, and the stimulated activity was more sensitive to inhibition by complex I inhibitors. HQNO (2-heptyl-4-hydroxyquinoline N-oxide) also stimulated the oxidation, and the stimulated respiration was more sensitive to KCN inhibition than uncoupler stimulated respiration. Fructose, among 20 sugars and sugar alcohols including glucose and mannose, was oxidized with a CO2/O2 ratio of 1.0 by the organism. Iron chelators in general stimulated endogenous respiration, but some of them reduced Fe3+ chemically, introducing complications. The results are discussed in view of a branched electron transport system of the organism and its possible control.Key words: Acidithiobacillus ferrooxidans, endogenous respiration, uncouplers, electron transport.

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