scholarly journals Electrostatic screening stimulates rate-limiting steps in mitochondrial electron transport

1984 ◽  
Vol 223 (3) ◽  
pp. 761-767 ◽  
Author(s):  
I M Møller ◽  
C J Kay ◽  
J M Palmer
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Active Site ◽  
Plant Mitochondria ◽  
Jerusalem Artichoke ◽  
Maximal Activity ◽  
Effective Concentration ◽  
Ph Optimum ◽  
Transport Chain ◽  
Rate Limiting

The effect of electrostatic screening of fixed negative charges on uncoupled mitochondrial electron transport was investigated with substrates with different charge and different sites of donation of electrons to the electron-transport chain of Jerusalem-artichoke (Helianthus tuberosus L.) mitochondria. Duroquinol (neutral substrate) was oxidized with a pH optimum of 7.6-7.8. The addition of cations caused a doubling of Vmax. (order of efficiency C3+ greater than C2+ greater than C+) through electrostatic screening, whereas the Km was unaffected. Screening stimulated (by 150%) the Vmax. for the oxidation of reduced cytochrome c (positive substrate; to O2), but in this case the Km doubled. The Vmax. of the oxidation of exogenous NADH (negative substrate) was also stimulated by screening when the acceptor was O2, but unaffected when duroquinone was the acceptor. In both cases, the Km for NADH was considerably decreased. The effect of screening on the Km for the different substrates can be explained by the changes in the effective concentration of substrate near the active site due to the lowering in the size of the surface potential. The effect of screening on the Vmax. of the different partial processes indicates that increasing the salt concentration of the medium enhances the maximal activity of cytochrome c oxidase. However, the results also point at the existence of other rate-limiting steps, which are affected by screening and may involve ubiquinone, in electron transport in plant mitochondria.

scholarly journals Charge screening by cations affects the conformation of the mitochondrial inner membrane. A study of exogenous NAD(P)H oxidation in plant mitochondria

1981 ◽  
Vol 195 (3) ◽  
pp. 583-588 ◽  
Author(s):  
I M Møller ◽  
J M Palmer
Keyword(s):  
Electron Transport ◽  
Protein Complexes ◽  
Plant Mitochondria ◽  
Lateral Diffusion ◽  
Jerusalem Artichoke ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Cations caused a decrease in the apparent Km and an increase in the Vmax. for the oxidation of exogenous NADH by both Jerusalem-artichoke (Helianthus tuberosus) and Arum maculatum (cuckoo-pint) mitochondria prepared and suspended in a low-cation medium (approximately or equal to 1 mM-K+). In Arum mitochondria the addition of cations caused a much greater stimulation of the oxidation of NAD(P)H via the cytochrome oxidase pathway than via the alternative, antimycin-insensitive, pathway. This shows that cations affected a rate-limiting step in the electron-transport chain at or beyond ubiquinone, the branch-point of electron transport in plant mitochondria. The effects were only dependent on the valency of the cation (efficiency C3+ greater than C2+ greater than C+) and not on its chemical nature, which is consistent with the theory of the diffuse layer. The results are interpreted to show that the screening of fixed negative membrane changes on lipids and protein complexes causes a conformational change in the mitochondrial inner membrane, leading to a change in a rate-limiting step of NAD(P)H oxidation. More specifically, it is proposed that screening removes electrostatic restrictions on lateral diffusion and thus accelerates diffusion-limited steps in electron transport.

scholarly journals Effects of L-Malate on Mitochondrial Oxidoreductases in Liver of Aged Rats

2011 ◽  
pp. 329-336 ◽  
Author(s):  
J.-L. WU ◽  
Q.-P. WU ◽  
Y.-P. PENG ◽  
J.-M. ZHANG
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Electron Transport Chain ◽  
Nadh Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Radical Scavenger ◽  
Aged Rats ◽  
Transport Chain ◽  
Nadh Cytochrome

Accumulation of oxidative damage has been implicated to be a major causative factor in the decline in physiological functions that occur during the aging process. The mitochondrial respiratory chain is a powerful source of reactive oxygen species (ROS), considered as the pathogenic agent of many diseases and aging. L-malate, a tricarboxylic acid cycle intermediate, plays an important role in transporting NADH from cytosol to mitochondria for energy production. Previous studies in our laboratory reported L-malate as a free radical scavenger in aged rats. In the present study we focused on the effect of L-malate on the activities of electron transport chain in young and aged rats. We found that mitochondrial membrane potential (MMP) and the activities of succinate dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats were significantly decreased when compared to young control rats. Supplementation of L-malate to aged rats for 30 days slightly increased MMP and improved the activities of NADH-dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats when compared with aged control rats. In young rats, L-malate administration increased only the activity of NADH-dehydrogenase. Our result suggested that L-malate could improve the activities of electron transport chain enzymes in aged rats

scholarly journals Stress signalling dynamics of the mitochondrial electron transport chain and oxidative phosphorylation system in higher plants

2019 ◽  
Vol 125 (5) ◽  
pp. 721-736 ◽  
Author(s):  
Corentin Dourmap ◽  
Solène Roque ◽  
Amélie Morin ◽  
Damien Caubrière ◽  
Margaux Kerdiles ◽  
...  
Keyword(s):  
Climate Change ◽  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Electron Transport Chain ◽  
Plant Mitochondria ◽  
Mitochondrial Electron Transport Chain ◽  
Oxidative Phosphorylation System ◽  
Transport Chain ◽  
Wide Range ◽  
Stress Signalling

Abstract Background Mitochondria play a diversity of physiological and metabolic roles under conditions of abiotic or biotic stress. They may be directly subjected to physico-chemical constraints, and they are also involved in integrative responses to environmental stresses through their central position in cell nutrition, respiration, energy balance and biosyntheses. In plant cells, mitochondria present various biochemical peculiarities, such as cyanide-insensitive alternative respiration, and, besides integration with ubiquitous eukaryotic compartments, their functioning must be coupled with plastid functioning. Moreover, given the sessile lifestyle of plants, their relative lack of protective barriers and present threats of climate change, the plant cell is an attractive model to understand the mechanisms of stress/organelle/cell integration in the context of environmental stress responses. Scope The involvement of mitochondria in this integration entails a complex network of signalling, which has not been fully elucidated, because of the great diversity of mitochondrial constituents (metabolites, reactive molecular species and structural and regulatory biomolecules) that are linked to stress signalling pathways. The present review analyses the complexity of stress signalling connexions that are related to the mitochondrial electron transport chain and oxidative phosphorylation system, and how they can be involved in stress perception and transduction, signal amplification or cell stress response modulation. Conclusions Plant mitochondria are endowed with a diversity of multi-directional hubs of stress signalling that lead to regulatory loops and regulatory rheostats, whose functioning can amplify and diversify some signals or, conversely, dampen and reduce other signals. Involvement in a wide range of abiotic and biotic responses also implies that mitochondrial stress signalling could result in synergistic or conflicting outcomes during acclimation to multiple and complex stresses, such as those arising from climate change.

The multiplicity of dehydrogenases in the electron transport chain of plant mitochondria

Mitochondrion ◽  
2008 ◽  
Vol 8 (1) ◽  
pp. 47-60 ◽  
Author(s):  
Allan G. Rasmusson ◽  
Daniela A. Geisler ◽  
Ian M. Møller
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Plant Mitochondria ◽  
Transport Chain

Possible role of free oxidation processes in the regulation of reactive oxygen species production in plant mitochondria

2003 ◽  
Vol 31 (6) ◽  
pp. 1316-1317 ◽  
Author(s):  
V.N. Popov
Keyword(s):  
Reactive Oxygen Species ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Plant Mitochondria ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Oxidation Processes ◽  
Transport Chain ◽  
Electron Reduction ◽  
Species Production

The non-coupled substrate oxidation mediated by components of the electron transport chain that are not coupled to energy accumulation (such as plant alternative oxidase and rotenone-insensitive NADH dehydrogenases) and uncoupled respiration are peculiar features of plant mitochondria. The physiological significance of such energy-wasting oxidation processes is still debated. It is proposed that non-coupled oxidation could regulate the level of reduction of components of the electron transport chain and the rate of one-electron reduction of oxygen, thereby affecting the rate of formation of reactive oxygen species.

scholarly journals Oxidation and reduction of pyridine nucleotides in alamethicin-permeabilized plant mitochondria

2004 ◽  
Vol 380 (1) ◽  
pp. 193-202 ◽  
Author(s):  
Fredrik I. JOHANSSON ◽  
Agnieszka M. MICHALECKA ◽  
Ian M. MØLLER ◽  
Allan G. RASMUSSON
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Nadh Dehydrogenase ◽  
Plant Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Transport Chain ◽  
Invasive Method

The inner mitochondrial membrane is selectively permeable, which limits the transport of solutes and metabolites across the membrane. This constitutes a problem when intramitochondrial enzymes are studied. The channel-forming antibiotic AlaM (alamethicin) was used as a potentially less invasive method to permeabilize mitochondria and study the highly branched electron-transport chain in potato tuber (Solanum tuberosum) and pea leaf (Pisum sativum) mitochondria. We show that AlaM permeabilized the inner membrane of plant mitochondria to NAD(P)H, allowing the quantification of internal NAD(P)H dehydrogenases as well as matrix enzymes in situ. AlaM was found to inhibit the electron-transport chain at the external Ca2+-dependent rotenone-insensitive NADH dehydrogenase and around complexes III and IV. Nevertheless, under optimal conditions, especially complex I-mediated NADH oxidation in AlaM-treated mitochondria was much higher than what has been previously measured by other techniques. Our results also show a difference in substrate specificities for complex I in mitochondria as compared with inside-out submitochondrial particles. AlaM facilitated the passage of cofactors to and from the mitochondrial matrix and allowed the determination of NAD+ requirements of malate oxidation in situ. In summary, we conclude that AlaM provides the best method for quantifying NADH dehydrogenase activities and that AlaM will prove to be an important method to study enzymes under conditions that resemble their native environment not only in plant mitochondria but also in other membrane-enclosed compartments, such as intact cells, chloroplasts and peroxisomes.

On the Reaction between Chlorophyll-a, and its Primary Electron Donors in Photosynthesis

1971 ◽  
Vol 26 (11) ◽  
pp. 1171-1174 ◽  
Author(s):  
W. Haehnel ◽  
G. Döring ◽  
H. T. Witt
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Equilibrium Constants ◽  
Reaction Times ◽  
Primary Electron ◽  
High Time Resolution ◽  
Chl A ◽  
Transport Chain ◽  
Rate Limiting ◽  
Reduced State

Electrons produced by Chl-aII in a short flash are finally transfered to Chl-ai after having passed several intermediates. The reaction between Chl-aI and its primary electron donators PD (probably Cyt-f and PC) has been studied by means of high time resolution flash photometry in isolated spinach chloroplasts with the following results:1. When PD are in the oxidized state, the reduction of Chl-aI⊕ takes place with the rate limiting reaction time of the electron transport chain (≈ 20 ms).2. When PD are in the reduced state, the reduction of Chl-aI⊕ takes place with the reaction times between the PD and Chl-ai. We found two half life times: one of about 200 μs and one of about 10 μs.The reduced state of PD is realized when weak monitoring light or hvII-preillumination is used.The two reaction times of ≈ 200 μs and of ≈ 10 µs are interpreted to represent the electron transfers between Cyt-f and Chl-aI and between PC and Chl-aI resp.Equilibrium constants of the electron transfer from PD to Chl-aI and the arrangement of the intermediates in the electron transport chain are discussed.

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