Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.9.3.1 (cytochrome oxidase)
8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Cytochrome oxidase was incorporated into preformed liposomes containing phosphatidylserine. When confronted with a mixture of liposomes, some containing phosphatidylserine and some without it, the enzyme was incorporated only into the phosphatidylserine-containing liposomes. 2. The hydrophobic proteins of the oligomycin-sensitive ATPase incubated in the presence of a mixture of liposomes with and without cytochrome oxidase were preferentially incorporated into cytochrome oxidase-containing liposomes. This selectivity was abolished by either cytochrome c or ascorbate. 3. Cytochrome oxidase incubated in the presence of a mixture of liposomes with and without the hydrophobic proteins of the ATPase was preferentially incorporated into liposomes that did not contain the hydrophobic proteins. 4. Cytochrome oxidase and the oligomycin-sensitive ATPase were preferentially incorporated into pure liposomes over bacteriorhodopsin-containing vesicles. 5. Reduced coenzyme Q (QH2)-cytochrome c reductase was incorporated randomly when incubated in the presence of a mixture of pure liposomes and liposomes containing the hydrophobic proteins of the ATPase complex. 6. The significance of the incorporation procedure as a model for membrane biogenesis is discussed.
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PMID:Selective incorporation of membrane proteins into proteoliposomes of different compositions. 19 31

Oxidation of exogenous NADH in mitochondria isolated from wild type and mi-1 mutant of Neurospora crassa decreases rapidly in vitro. In mi-1 mutant mitochondria the inactivation concerns the alternate pathway of oxidation whereas in the wild type it involves an unknown component of the respiratory chain. The activity of the primary NADH dehydrogenase is constant within the time of the experiments (2-4 h). NADH oxidase is not inactivated if oxygen is removed from the incubation medium by nitrogen bubbling. Succinate oxidase does not show any remarkable changes in activity within 2-3 h. In fresh mitochondria of the mi-1 mutant reduced ubiquinone is completely reoxidized by cytochrome oxidase but only 80% reoxidized by the alternate oxidase. In aged mitochondria of the mi-1 mutant in the presence of cyanide, ubiquinone is reduced to the level characteristic for fresh mitochondria in which respiration is completely inhibited by cyanide plus salicylhydroxamic acid. In these mitochondria the reoxidation of the reduced ubiquinone proceeds only via the cytochrome pathway. It is supposed that a labile component(s) of the respiratory chain present in the mi-1 mutant and the wild type mitochondria may, in mi-1 mutant, act as an alternate oxidase.
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PMID:Disappearance of the cyanide-insensitive pathway of oxidation in mitochondria of MI-1 mutant of Neurospora crassa in vitro. 20 34

The cytochrome o complex of Escherichia coli is a ubiquinol oxidase which is the predominant respiratory terminal oxidase when the bacteria are grown under high oxygen tension. The amino acid sequences of three of the subunits of this quinol oxidase reveal a substantial relationship to the aa3-type cytochrome c oxidases. The two cytochrome components (b563.5 and o) and the single copper (CuB) present in the E. coli quinol oxidase appear to be equivalent to cytochrome a, cytochrome a3, and CuB of the aa3-type cytochrome c oxidases, respectively. These three prosthetic groups are all located within subunit I of the oxidase. Sequence alignments indicate only six totally conserved histidine residues among all known sequences of subunit I of the cytochrome c oxidases of various species plus the E. coli quinol oxidase. Site-directed mutagenesis has been used to change each of these totally conserved histidines with the presumption that two of these six must ligate to the low spin cytochrome center of the E. coli oxidase. The presence of the low spin cytochrome b563.5 component of the oxidase can be evaluated both by visible absorbance properties and by its EPR spectrum. The results unambiguously indicate that His-106 and His-421 are the ligands of the six-coordinate low spin cytochrome b563.5. Although the data are not definitive in making additional metal ligation assignments of the remaining four totally conserved histidines, a reasonable model is suggested for the structure of the catalytic core of the cytochrome o complex and, by extrapolation, of cytochrome c oxidase.
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PMID:Determination of the ligands of the low spin heme of the cytochrome o ubiquinol oxidase complex using site-directed mutagenesis. 130 9

The interaction between cytochrome c oxidase complex and adenosine triphosphate synthase (F1F0) complex in the purified, dispersed state and embedded in phospholipid vesicles was studied by differential scanning calorimetry and by spin-label electron paramagnetic resonance. The detergent-dispersed cytochrome oxidase and F1F0 complexes undergo endothermic thermodenaturation. However, when these complexes are embedded in phospholipid vesicles, they undergo exothermic thermodenaturation. The energy released is believed to result from the collapse of a strained interaction between unsaturated fatty acyl groups of phospholipids and an exposed area of the complex formed by the removal of interacting proteins. The exothermic enthalpy change of thermodenaturation of a protein-phospholipid exothermic enthalpy change of thermodenaturation of a protein-phospholipid vesicle containing both cytochrome oxidase complex and F1F0 was smaller than that of a mixture of protein-phospholipid vesicles formed from each individual electron transfer complex. This suggests specific interaction between cytochrome oxidase complex and F1F0 in the membrane. Further evidence for interaction between these two complexes is provided by saturation transfer EPR studies in which the rotational correlation time of spin-labeled cytochrome oxidase increases significantly when the complex is mixed with F1F0 prior to being embedded in phospholipid vesicles. From these results, it is concluded that at least a part of cytochrome oxidase and a part of F1F0 form a supermacromolecular complex in the inner mitochondrial membrane. No such supermacromolecular complex is detected between F1F0 and ubiquinol--cytochrome c reductase.
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PMID:Spin-label electron paramagnetic resonance and differential scanning calorimetry studies of the interaction between mitochondrial cytochrome c oxidase and adenosine triphosphate synthase complex. 131 90

The orientation of the two haems of the Escherichia coli ubiquinol oxidase:O2 reductase, cytochrome bo, has been determined by electron paramagnetic resonance studies on oriented multilayer preparations of cytoplasmic membrane fragments. The enzyme contains a low-spin b-like haem and a high-spin b-like haem, designated cytochromes b and o respectively. Both haems are oriented with their planes perpendicular to the membrane plane, further extending the catalogue of structural and functional similarities between this enzyme and the mammalian cytochrome c oxidase, cytochrome aa3.
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PMID:Orientation of the haems of the ubiquinol oxidase:O2 reductase, cytochrome bo of Escherichia coli. 164 21

Rats treated with hydroxycobalamin[c-lactam] (HCCL), a cobalamin analogue that induces methylmalonic aciduria, have increased hepatic mitochondrial content and increased oxidative metabolism of pyruvate and palmitate per hepatocyte. The present studies were undertaken to characterize oxidative metabolism in isolated liver mitochondria from rats treated with HCCL. After 5-6 weeks, state 3 oxidation rates for diverse substrates are reduced in mitochondria from HCCL-treated rats. Similar reductions of mitochondrial oxidation rates are obtained with dinitrophenol-uncoupled mitochondria excluding defective phosphorylation as a cause for the observed decrease in mitochondrial oxidation. The activities of mitochondrial oxidases are reduced in HCCL-treated rats and demonstrate a defect in complex IV. Investigation of the complexes of the respiratory chain reveals a 32% decrease of ubiquinol:ferricytochrome c oxidoreductase (complex III) activity and a 72% decrease of ferrocytochrome c:oxygen oxidoreductase (complex IV) activity in mitochondria from 5-6-week HCCL-treated rats as compared with controls. Liver mitochondria from HCCL-treated rats also demonstrate decreased cytochrome content per mg of mitochondrial protein (25% decrease of cytochrome b and 52% decrease of cytochrome a + a3 as compared with control rats). The HCCL-treated rat represents an animal model for the study of the consequences of respiratory chain defects in liver mitochondria.
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PMID:Decreased activities of ubiquinol:ferricytochrome c oxidoreductase (complex III) and ferrocytochrome c:oxygen oxidoreductase (complex IV) in liver mitochondria from rats with hydroxycobalamin[c-lactam]-induced methylmalonic aciduria. 165 42

We report the first lateral diffusion measurements of redox components in normal-sized, matrix-containing, intact mitoplasts (inner membrane-matrix particles). The diffusion measurements were obtained by submicron beam fluorescence recovery after photobleaching measurements of individual, intact, rat liver mitoplasts bathed in different osmolarity media to control the matrix density and the extent of inner membrane folding. The data reveal that neither the extent of mitochondrial matrix density nor the complexity of the inner membrane folding have a significant effect on the mobility of inner membrane redox components. Diffusion coefficients for Complex I (NADH:ubiquinone oxidoreductase), Complex III (ubiquinol: cytochrome c oxidoreductase), Complex IV (cytochrome oxidase), ubiquinone, and phospholipid were found to be effectively invariant with the matrix density and/or membrane folding and essentially the same as values we reported previously for spherical, fused, ultralarge, matrix-free, inner membranes. Diffusion of proton-transporting Complex V (ATP synthase) appeared to be 2-3-fold slower at the greatest matrix density and degree of membrane folding. Consistent with a diffusion-coupled mechanism of electron transport, comparison of electron transport frequencies (productive collisions) with the theoretical, diffusion-controlled, collision frequencies (maximum collisions possible) revealed that there were consistently more calculated than productive collisions for all redox partners. Theoretical analyses of parameters for submicron fluorescence recovery after photobleaching measurements in intact mitoplasts support the finding of highly mobile redox components diffusing at the same rates as determined in conventional fluorescence recovery after photobleaching measurements in fused, ultralarge inner membranes. These findings support the Random Collision Model of Mitochondrial Electron Transport at the level of the intact mitoplast and suggest a similar conclusion for the intact mitochondrion.
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PMID:Lateral diffusion of redox components in the mitochondrial inner membrane is unaffected by inner membrane folding and matrix density. 200 33

Under anaerobic circumstances in the presence of nitrate Paracoccus denitrificans is able to denitrify. The properties of the reductases involved in nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase are described. For that purpose not only the properties of the enzymes of P. denitrificans are considered but also those from Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas stutzeri. Nitrate reductase consists of three subunits: the alpha subunit contains the molybdenum cofactor, the beta subunit contains the iron sulfur clusters, and the gamma subunit is a special cytochrome b. Nitrate is reduced at the cytoplasmic side of the membrane and evidence for the presence of a nitrate-nitrite antiporter is presented. Electron flow is from ubiquinol via the specific cytochrome b to the nitrate reductase. Nitrite reductase (which is identical to cytochrome cd1) and nitrous oxide reductase are periplasmic proteins. Nitric oxide reductase is a membrane-bound enzyme. The bc1 complex is involved in electron flow to these reductases and the whole reaction takes place at the periplasmic side of the membrane. It is now firmly established that NO is an obligatory intermediate between nitrite and nitrous oxide. Nitrous oxide reductase is a multi-copper protein. A large number of genes is involved in the acquisition of molybdenum and copper, the formation of the molybdenum cofactor, and the insertion of the metals. It is estimated that at least 40 genes are involved in the process of denitrification. The control of the expression of these genes in P. denitrificans is totally unknown. As an example of such complex regulatory systems the function of the fnr, narX, and narL gene products in the expression of nitrate reductase in E. coli is described. The control of the effects of oxygen on the reduction of nitrate, nitrite, and nitrous oxide are discussed. Oxygen inhibits reduction of nitrate by prevention of nitrate uptake in the cell. In the case of nitrite and nitrous oxide a competition between reductases and oxidases for a limited supply of electrons from primary dehydrogenases seems to play an important role. Under some circumstances NO formed from nitrite may inhibit oxidases, resulting in a redistribution of electron flow from oxygen to nitrite. P. denitrificans contains three main oxidases: cytochrome aa3, cytochrome o, and cytochrome co. Cytochrome o is proton translocating and receives its electrons from ubiquinol. Some properties of cytochrome co, which receives its electrons from cytochrome c, are reported.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolic regulation including anaerobic metabolism in Paracoccus denitrificans. 205 Jun 53

Two cytochrome b respiratory-deficient mutants were sequenced and their DNA base change identified, leading to the replacement of glycine (G137 by valine or glutamic acid. No variation in their cytochrome b content with regard to cytochrome oxidase and cytochrome (c + c1) was found to have occurred. Their cellular respiratory activity with various substrates was partly conserved and was totally inhibited by antimycin A. Their ubiquinol (QH2)-cytochrome c reductase/mole cytochrome b activity decreased by about 50%. Paradoxically their growth on respiratory substrate was abolished. Both mutants retained a high-affinity binding site for antimycin A, and exhibited a myxothiazol-resistance at the mitochondrial level. It seems likely that the mutated position (137), which belongs to the ubiquinol oxidizing domain of the bc1 complex, interferes, directly or indirectly, with the respiratory growth capacity of the cell.
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PMID:Two substitutions at the same position in the mitochondrial cytochrome b gene of S. cerevisiae induce a mitochondrial myxothiazol resistance and impair the respiratory growth of the mutated strains abbeit maintaining a good electron transfer activity. 207 67

Using the principle of specific vectorial ligand conduction, we outline directly coupled protonmotive O loop and O cycle mechanisms of cytochrome oxidase action that are analogous to protonmotive Q loop and Q cycle mechanisms of QH2 dehydrogenase action. We discuss these directly coupled mechanisms in the light of available experimental knowledge, and suggest that they may stimulate useful new research initiatives designed to elucidate the osmochemistry of protonmotive oxygen reduction in cytochrome oxidase.
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PMID:Chemiosmotic coupling in cytochrome oxidase. Possible protonmotive O loop and O cycle mechanisms. 241 Feb 91


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