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)

We have cloned and sequenced over 9 kb of the mitochondrial genome from the sea star Pisaster ochraceus. Within a continuous 8.0-kb fragment are located the genes for NADH dehydrogenase subunits 1, 2, 3, and 4L (ND1, ND2, ND3, and ND4L), cytochrome oxidase subunits I, II, and III (COI, COII, and COIII), and adenosine triphosphatase subunits 6 and 8 (ATPase 6 and ATPase 8). This large fragment also contains a cluster of 13 tRNA genes between ND1 and COI as well as the genes for isoleucine tRNA between ND1 and ND2, arginine tRNA between COI and ND4L, lysine tRNA between COII and ATPase 8, and the serine (UCN) tRNA between COIII and ND3. The genes for the other five tRNAs lie outside this fragment. The gene for phenylalanine tRNA is located between cytochrome b and the 12S ribosomal genes. The genes for tRNA(glu) and tRNA(thr) are 3' to 12S ribosomal gene. The tRNAs for histidine and serine (AGN) are adjacent to each other and lie between ND4 and ND5. These data confirm the novel gene order in mitochondrial DNA (mtDNA) of sea stars and delineate additional distinctions between the sea star and other mtDNA molecules.
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PMID:Nucleotide sequence of nine protein-coding genes and 22 tRNAs in the mitochondrial DNA of the sea star Pisaster ochraceus. 197 16

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

The effects of butylated hydroxyanisole (BHA), a commonly used food antioxidant, on oxygen consumption, ATPase activity, and the redox state of some electron carriers of rat liver mitochondria have been studied. It was observed that BHA slightly stimulated state 4 respiration but strongly inhibited ADP- and uncoupler-stimulated respiration on NAD(+)- and FAD-linked substrates. ATPase activity and vectorial H+ ejection were affected only slightly by BHA, suggesting that BHA predominantly inhibits mitochondrial electron flow. Experiments to determine its site of action showed that BHA did not noticeably affect electron flow through cytochrome oxidase; in contrast, NADH:duroquinone reductase activity and electron flow through ubiquinone-cytochrome b-cytochrome c complex were inhibited strongly because the oxidation of duroquinol was affected markedly. The BHA block of electron transport was bypassed by both N,N,N',N'-tetramethyl-p-phenylenediamine and 2,6-dichlorophenolindophenol. Also, the presence of BHA changed the redox state of cytochrome b and c1 to a more oxidized level. These observations suggest that electron transport is inhibited by BHA at the NADH-ubiquinone and at the ubiquinone-cytochrome b levels. From Hill plots, it is clear that more than one binding site is involved in complete inhibition; in addition, available evidence suggests that there may be two sites at the substrate side of ubiquinone and another two sites at the oxygen side of ubiquinone. Consequently, mitochondrial ATP synthesis would be interrupted. This event could be related to the toxicity of BHA.
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PMID:Effect of butylated hydroxyanisole on electron transport in rat liver mitochondria. 214 54

The steady state levels of mitochondrial rRNAs, 5 tRNAs, the 9 S RNA, and the RNA products from the genes coding for subunits 6 and 9 of the ATP synthase, cytochrome b, and subunit 1 of cytochrome oxidase have been determined after growth of yeast under conditions of respiratory repression or derepression. The analysis indicates that the mitochondrial rRNAs are present in 2000 or 9000 copies/cell in repressed or derepressed yeast, respectively. The levels of the other RNAs also differed to a similar extent, with the exception of the level of the tRNAfMet which differs by only 1.7-fold. The levels of the individual protein coding RNAs varied from 480 copies/cell for the Oli-1 RNA to 100 copies/cell for the Oli-2 RNA under derepressive conditions and from 130 copies/cell to 33 copies/cell for the same RNAs in glucose repressive conditions. The levels of the tRNAs varied even more markedly, ranging from 4200 copies/cell for the tRNAPhe to 240 copies/cell for the tRNACys after growth in derepressive conditions and from 800 copies/cell for the tRNAfMet to 30 copies/cell for the tRNACys of glucose repressed yeast. These results indicate that glucose repression uniformly decreases the levels of the individual mitochondrial RNAs studied. This decrease is related to a lower synthesis of mitochondrial RNA in the glucose repressed cells as compared to derepressed cells.
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PMID:Steady state analysis of mitochondrial RNA after growth of yeast Saccharomyces cerevisiae under catabolite repression and derepression. 242 12

The mitochondrial respiratory system is absent in slender bloodstream forms of Trypanosoma brucei, incomplete in stumpy bloodstream forms, and complete in procyclic (insect) forms. The steady-state abundance of transcripts of some mitochondrially encoded components of the respiratory system correlates with its differential expression in different life cycle stages. Recently, it was reported that uridines which are not encoded in the genome are added to cytochrome b and cytochrome oxidase II transcripts. We now report that the (U)+ transcripts of both genes are found in procyclic forms and to some degree in stumpy forms but are absent in slender forms. The uridine additions to cytochrome oxidase II correct a frameshift in the gene and presumably allow production of a full-length protein, whereas those added to cytochrome b create an in-frame AUG which extends the N terminus of the predicted protein by 20 amino acids. The stage specificity of uridine additions to these transcripts thus reflects the life cycle stage during which the protein products would be used. Transcripts of MURF2, a gene of unknown function, have additional uridines in both slender and procyclic forms which create two in-frame AUGs. MURF2 transcripts additionally differ from the DNA sequence in ways which cannot be explained by uridine addition alone, implying that other processes alter these transcripts.
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PMID:Developmental aspects of uridine addition within mitochondrial transcripts of Trypanosoma brucei. 245 74

The effect of rhein on the oxygen consumption, oxidative phosphorylation, ATPase activity and redox state of electron carriers of rat liver mitochondria has been studied. Rhein inhibits ADP- and uncoupler-stimulated respiration on various NAD-linked substrates and succinate, but stimulates state 4 respiration of mitochondria respiring on succinate. Experiments on specific segments of the respiratory chain showed that rhein does not inhibit electron flow through cytochrome oxidase. Electron flow through site 2, the ubiquinone-cytochrome b-cytochrome c1 complex, was also unaffected by rhein, which failed to inhibit the oxidation of duroquinol. Rhein affects oxidative phosphorylation by inhibiting both electron transfer and ADP-driven H+ uptake. The inhibition of succinate oxidation by rhein was found to take place at a point between succinate and ubiquinone, perhaps at the level of succinic dehydrogenase. Spectroscopic evidence demonstrated that rhein induces a NAD(P)H oxidation in mitochondria respiring either on endogenous substrates or on glutamate + malate, and an inhibition of the cytochrome b reduction by succinate. These observations, together with other evidence, suggest that rhein inhibits electron transport in rat liver mitochondria at the dehydrogenase-coenzyme level, particularly when the electron carriers are in a relatively oxidized state and/or when the inner membrane-matrix compartment is in the condensed state.
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PMID:Sites of inhibition of mitochondrial electron transport by rhein. 252 79

The cytochrome-bo quinol oxidase of Escherichia coli contains a high-spin b-type heme (cytochrome o), a low-spin b-type heme (cytochrome b) and copper. The EPR signal from cytochrome o is axial high spin and when titrated potentiometrically gives a bell-shaped curve. The low-potential side of this curve (Em7 approx. 160 mV) corresponds to the reduction/oxidation of the cytochrome. The high-potential side (Em7 approx. 350 mV) is proposed to be due to reduction/oxidation of a copper center; in the CuII form tight cytochrome o-copper spin coupling results in a net even spin system and loss of the EPR spectrum. Optical spectra of the alpha-bands of the reduced cytochromes at 77 K show that cytochrome b has its maxima at 564 nm when cytochrome o is oxidized but that this shifts to 561 nm when cytochrome o (max. 555 nm) is reduced. Both a heme-copper (cytochrome o-CuII) and a heme-heme (cytochrome o-cytochrome b) interaction are indicated in this quinol oxidase. These results indicate that cytochrome-bo quinol oxidase has a binuclear heme-copper catalytic site and suggest striking structural similarity to subunit I of the cytochrome aa3 system.
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PMID:Potentiometric titration of cytochrome-bo type quinol oxidase of Escherichia coli: evidence for heme-heme and copper-heme interaction. 254 43

A 19-year-old man born with thyroprivic hypothyroidism, due to congenital development defect, manifested hypogonadism, stunted growth, chronic progressive external ophthalmoplegia (CPEO), diffuse muscle weakness and wasting, right bundle branch block, cerebral atrophy. Muscle biopsy showed mitochondrial abnormalities. Biochemical investigations on muscle disclosed partial (50%) cytochrome c oxidase deficiency, 58% decrease of cytochrome aa3 and 41% decrease of cytochrome b. Enzyme-linked immunosorbent assay showed decrease of the immunologically active enzyme protein.
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PMID:Endocrine involvement in mitochondrial encephalomyopathy with partial cytochrome c oxidase deficiency. 254 Feb 84

The yeast box-mutant W7 exhibits deficiencies in cytochrome b and in nuclear coded complex III subunits, a phenotype observed previously in a patient with mitochondrial myopathy. DNA sequence analysis of mutant W7 revealed a single base transition in the cytochrome b gene; the mutated residue Gly 131 is perfectly conserved in all known cytochromes b and belongs to the Qo domain. Mutant W7 provides a model system for evaluating the action of therapeutic agents, such as vitamin K3 which restored NADH-oxidase activity in the mutant as well as in the antimycin-inhibited wild type. However, with the mutant, a greater quantity of menadione was necessary due to a decrease in other complex activities, and a much lower electron-flow fraction passed through cytochrome oxidase.
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PMID:Electron-transfer restoration by vitamin K3 in a complex III-deficient mutant of S. cerevisiae and sequence of the corresponding cytochrome b mutation. 255 31


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