scholarly journals Structure of the Zymomonas mobilis respiratory chain: oxygen affinity of electron transport and the role of cytochrome c peroxidase

Microbiology ◽  
2014 ◽  
Vol 160 (9) ◽  
pp. 2045-2052 ◽  
Author(s):  
Elina Balodite ◽  
Inese Strazdina ◽  
Nina Galinina ◽  
Samantha McLean ◽  
Reinis Rutkis ◽  
...  
Keyword(s):  
Electron Transport ◽  
Respiratory Chain ◽  
Peroxidase Activity ◽  
Zymomonas Mobilis ◽  
Alternative Oxidase ◽  
Oxygen Affinity ◽  
Aerobic Growth ◽  
Nadh Peroxidase ◽  
Kinetics Of

The genome of the ethanol-producing bacterium Zymomonas mobilis encodes a bd-type terminal oxidase, cytochrome bc 1 complex and several c-type cytochromes, yet lacks sequences homologous to any of the known bacterial cytochrome c oxidase genes. Recently, it was suggested that a putative respiratory cytochrome c peroxidase, receiving electrons from the cytochrome bc 1 complex via cytochrome c 552, might function as a peroxidase and/or an alternative oxidase. The present study was designed to test this hypothesis, by construction of a cytochrome c peroxidase mutant (Zm6-perC), and comparison of its properties with those of a mutant defective in the cytochrome b subunit of the bc 1 complex (Zm6-cytB). Disruption of the cytochrome c peroxidase gene (ZZ60192) caused a decrease of the membrane NADH peroxidase activity, impaired the resistance of growing culture to exogenous hydrogen peroxide and hampered aerobic growth. However, this mutation did not affect the activity or oxygen affinity of the respiratory chain, or the kinetics of cytochrome d reduction. Furthermore, the peroxide resistance and membrane NADH peroxidase activity of strain Zm6-cytB had not decreased, but both the oxygen affinity of electron transport and the kinetics of cytochrome d reduction were affected. It is therefore concluded that the cytochrome c peroxidase does not terminate the cytochrome bc 1 branch of Z. mobilis, and that it is functioning as a quinol peroxidase.

scholarly journals Electron transport in mitochondria isolated from the flagellate Polytomella caeca

1968 ◽  
Vol 107 (6) ◽  
pp. 829-837 ◽  
Author(s):  
D Lloyd ◽  
B. Chance
Keyword(s):  
Electron Transport ◽  
Spectral Data ◽  
Respiratory Chain ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Antimycin A ◽  
Fluorescence Emission Spectra ◽  
Sensitive Site ◽  
Kinetics Of ◽  
Transport In Mitochondria

1. Mitochondria isolated from Polytomella caeca contain cytochromes b, c+c1 and a+a3 and several flavoprotein species. 2. Electron transport is inhibited by antimycin A, rotenone, piericidin A and cyanide. 3. Spectral data indicate that antimycin A inhibits the reoxidation of reduced cytochrome b. 4. Various types of flavoprotein are characterized by simultaneous spectrophotometric and fluorimetric measurements on antimycin A-inhibited preparations and also by their absorption and fluorescence-emission spectra. 5. The rotenone-sensitive site lies between the two flavoproteins of the respiratory chain, designated FpD1 and FpD2. 6. Other flavoprotein species detected include those involved in the oxidation of succinate and externally added NADH; a large proportion of mitochondrial flavine is reduced by dithionite but not by known respiratory substrates. 7. The kinetics of flavoprotein and cytochrome reactions were studied.

scholarly journals Comparison of the Kinetic Parameters of Alternative Oxidases From Trypanosoma brucei and Arabidopsis thaliana—A Tale of Two Cavities

2021 ◽  
Vol 12 ◽  
Author(s):  
Fei Xu ◽  
Alice C. Copsey ◽  
Luke Young ◽  
Mario R. O. Barsottini ◽  
Mary S. Albury ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Kinetic Parameters ◽  
Trypanosoma Brucei ◽  
Alternative Oxidase ◽  
General Structure ◽  
Oxygen Affinity ◽  
Catalytic Efficiency ◽  
Hydrophobic Cavity ◽  
Keto Acids ◽  
Kinetics Of

The alternative oxidase (AOX) is widespread in plants, fungi, and some protozoa. While the general structure of the AOX remains consistent, its overall activity, sources of kinetic activation and their sensitivity to inhibitors varies between species. In this study, the recombinant Trypanosoma brucei AOX (rTAO) and Arabidopsis thaliana AOX1A (rAtAOX1A) were expressed in the Escherichia coli ΔhemA mutant FN102, and the kinetic parameters of purified AOXs were compared. Results showed that rTAO possessed the highest Vmax and Km for quinol-1, while much lower Vmax and Km were observed in the rAtAOX1A. The catalytic efficiency (kcat/Km) of rTAO was higher than that of rAtAOX1A. The rTAO also displayed a higher oxygen affinity compared to rAtAOX1A. It should be noted that rAtAOX1a was sensitive to α-keto acids while rTAO was not. Nevertheless, only pyruvate and glyoxylate can fully activate Arabidopsis AOX. In addition, rTAO and rAtAOX1A showed different sensitivity to AOX inhibitors, with ascofuranone (AF) being the best inhibitor against rTAO, while colletochlorin B (CB) appeared to be the most effective inhibitor against rAtAOX1A. Octylgallate (OG) and salicylhydroxamic acid (SHAM) are less effective than the other inhibitors against protist and plant AOX. A Caver analysis indicated that the rTAO and rAtAOX1A differ with respect to the mixture of polar residues lining the hydrophobic cavity, which may account for the observed difference in kinetic and inhibitor sensitivities. The data obtained in this study are not only beneficial for our understanding of the variation in the kinetics of AOX within protozoa and plants but also contribute to the guidance for the future development of phytopathogenic fungicides.

scholarly journals Respiratory Chain Analysis of Zymomonas mobilis Mutants Producing High Levels of Ethanol

2012 ◽  
Vol 78 (16) ◽  
pp. 5622-5629 ◽  
Author(s):  
Takeshi Hayashi ◽  
Tsuyoshi Kato ◽  
Kensuke Furukawa
Keyword(s):  
Ethanol Production ◽  
Dehydrogenase Activity ◽  
Respiratory Chain ◽  
Zymomonas Mobilis ◽  
Nadh Dehydrogenase ◽  
Nucleotide Sequence Analysis ◽  
Wild Type ◽  
Aerobic Growth ◽  
Content Type ◽  
Respiratory Chains

ABSTRACTWe previously isolated respiratory-deficient mutant (RDM) strains ofZymomonas mobilis, which exhibited greater growth and enhanced ethanol production under aerobic conditions. These RDM strains also acquired thermotolerance. Morphologically, the cells of all RDM strains were shorter compared to the wild-type strain. We investigated the respiratory chains of these RDM strains and found that some RDM strains lost NADH dehydrogenase activity, whereas others exhibited reduced cytochromebd-type ubiquinol oxidase or ubiquinol peroxidase activities. Complementation experiments restored the wild-type phenotype. Some RDM strains seem to have certain mutations other than the corresponding respiratory chain components. RDM strains with deficient NADH dehydrogenase activity displayed the greatest amount of aerobic growth, enhanced ethanol production, and thermotolerance. Nucleotide sequence analysis revealed that all NADH dehydrogenase-deficient strains were mutated within thendhgene, which includes insertion, deletion, or frameshift. These results suggested that the loss of NADH dehydrogenase activity permits the acquisition of higher aerobic growth, enhanced ethanol production, and thermotolerance in this industrially important strain.

The Role of Ubiquinone-10 in Cyclic Electron Transport in Rhodopsendomonas capsulata Ala pho+: Effects of Lyophilization and Extraction

1978 ◽  
Vol 33 (9-10) ◽  
pp. 704-711 ◽  
Author(s):  
John R. Bowyer ◽  
Assunta Baccarini-Melandri ◽  
B. Andrea Melandri ◽  
Antony R. Crofts
Keyword(s):  
Electron Transport ◽  
Reaction Center ◽  
Cytochrome B ◽  
Rhodopseudomonas Capsulata ◽  
Redox Mediators ◽  
Ferrocytochrome C ◽  
Ubiquinone 10 ◽  
Kinetics Of ◽  
Stimulation Of

Abstract 1. The effects of lyophilization and the extraction of ubiquinone-10 on the kinetics of electron transport in Rhodopseudomonas capsulata Ala pho+ have been investigated.2. Lyophilization reduced the amount of ferrocytochrome c2 photo-oxidized on a microsecond time scale following a single excitation.3. Lyophilization increased the reactivity of the electron transfer components with redox mediators, particularly N-methyl phenazonium methosulphate (PMS). At a concentration of 1 µᴍ , PMS accelerated reaction center re-reduction, ferricytochrome c2 re-reduction and ferrocytochrome b50 oxidation. The cytochrome c2 re-reduction stimulated by PMS was antimycin A insensitive but the cytochrome b50 oxidation was partially antim ycin sensitive.4. Removal of 25- 30 molecules of ubiquinone 10 per reaction center removed a secondary acceptor pool, had very little effect on the kinetics of ferricytochrome b50 reduction and ferricyto­ chrome c2 re-reduction, but markedly inhibited ferrocytochrome b50 oxidation. Ubiquinone extraction also caused an increased stimulation of ferrocytochrome b50 oxidation by PMS.5. The involvement of tightly bound ubiquinone in cytochrome b reduction and in the cytochrome b-c2 oxido-reductase, and the role of semiquinone species is discussed.

Energy transduction in the mitochondrionlike bacterium Paracoccus denitrificans during carbon- or sulphate-limited aerobic growth in continuous culture

1978 ◽  
Vol 56 (1) ◽  
pp. 13-22 ◽  
Author(s):  
H. G. Lawford
Keyword(s):  
Growth Rate ◽  
Electron Transport ◽  
Continuous Culture ◽  
Respiratory Chain ◽  
Paracoccus Denitrificans ◽  
Proton Translocation ◽  
Short Interval ◽  
Specific Inhibitor ◽  
Growth Yield ◽  
Aerobic Growth

Paracoccus denitrificans was grown in carbon-limited aerobic continuous culture (critical dilution rate (Dc) = 0.48 h−1). The molar growth yield for carbon (succinate or malate) was constant at about 60 over a broad dilution range (growth rate) from 0.10 to 0.48 h−1. Measurements of the stoichiometry of proton translocation associated with the oxidation of endogenous substrates yielded a ratio of protons ejected from the cell per atom of oxygen consumed (→H+:O) of 8.55 which decreased to 5.85 in the presence of piericidin A (PA), a specific inhibitor of NADH dehydrogenase (EC 1.6.99.3). With starved cells, the observed →H+:O associated with the oxidation of added succinate in the presence of PA was 5.61. These observed →H+:O's represent an underestimation since no correction was made for proton backflow during the short interval of respiratory activity. Aerobic growth of Pc. denitrificans in the chemostat becomes sulphate limited at entering concentrations of sulphate <300 μM. Neither the maximum specific growth rate (measured at Dc) nor the observed molar growth yield for succinate decreased under sulphate limitation. The NADH oxidase in electron transport particles prepared from sulphate-limited cells was completely inhibited by PA. The stoichiometry of proton translocation associated with malate oxidation was similarly unaffected by sulphate limitation. It is concluded that (a) the respiratory chain of aerobic, heterotrophically grown Pc. denitrificans possesses three sites of energy conservation, including site III, (b) the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling site is 3, and (c) that sulphate limitation does not lead to a loss of proton translocation associated with the cytochrome-independent region of the respiratory chain.

The role of ligands in electron transport in nanocrystal solids

Nanoscale ◽  
2020 ◽  
Vol 12 (45) ◽  
pp. 23028-23035
Author(s):  
Artem R. Khabibullin ◽  
Alexander L. Efros ◽  
Steven C. Erwin
Keyword(s):  
Electron Transport ◽  
Theoretical Modeling

Theoretical modeling of wavefunction overlap in nanocrystal solids elucidates the important role played by ligands in electron transport.

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