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PubMed1992

RNA Editing of Cytochrome Oxidase Subunit III in Sunflower Mitochondria.

Direct sequencing of cytochrome oxidase subunit III (coxIII) mRNA with a specific primer confirms RNA editing in sunflower (Helianthus annus) mitochondria. Six instances of mRNA editing could be verified, one of these specific to this species. All the editing events involve C to U transitions in the coxIII mRNA causing codon changes that lead to amino acids better conserved in evolution than those encoded in the genomic DNA. This observation confirms RNA editing to be widespread in higher plant mitochondria.

Journal Article↗
PubMed1989

Activity distribution of cytochrome oxidase in the rat retina. A quantitative histochemical study.

Cytochrome oxidase (CYO) is a key enzyme in the respiratory chain. Therefore, CYO has an important role in the cell metabolism. In the present study CYO activity in the rat retina was identified by histochemical staining. The density of the staining, corresponding to the activity of the CYO, was evaluated quantitatively by densitometry. A high CYO activity was found in the retinal pigment epithelium, in the inner segment of the photoreceptors, in the outer plexiform layer and in the inner plexiform layer. In the outer segment of the photoreceptors, in the outer nuclear layer, and in the inner nuclear layer the CYO activity was relatively low. An analysis of variance demonstrated that the precision in an estimation of a mean depends on the number of animals and the number of retinal sections per animal.

Animals↗
PubMed1989

Electron transfer process in cytochrome oxidase after pulse radiolysis.

The reduction of bovine heart cytochrome oxidase by the 1-methylnicotinamide (MNA) radical was investigated by the use of pulse radiolysis. With the decay of the MNA radical, the absorption at 445 and 605 nm, a characteristic to ferrous heme a of the oxidase, increased. The kinetic difference spectrum obtained was similar to that of the fully reduced minus the fully oxidized form of the oxidase, and was not different from that obtained in the reaction of the MNA radical with the mixed valence CO complex of the oxidase, where heme a3 is the CO-bound reduced form with heme a oxidized. This suggests that the absorption changes at 445 and 605 nm arise from the reduction of heme a, not heme a3. In order to elucidate the contribution of "visible" copper in this reaction, the absorption of the oxidase in the near-infrared region was measured. A decrease of the 830 nm band due to the reduction of visible copper was detected with a half-life of 5 microseconds. This absorption change obeyed pseudo-first order kinetics and its rate constant increased with the concentration of the oxidase. This suggests that the absorption change at 830 nm is followed by a bimolecular reaction of the MNA radical with visible copper of the oxidase. After the first phase of the reduction, the return of the 830 nm band corresponding to oxidation of the copper was observed with a half-life of 100 microseconds. Concomitantly, the absorption at 605 and 445 nm due to the reduction of heme a increased. The rates of oxidation of the copper were identical to those of the reduction of heme a and independent of the oxidase concentration. This suggests that the MNA radical reacts with visible copper of the oxidase with a second order rate constant of 1.5 X 10(9) m-1 s-1 and subsequently the electron flows to heme a by intramolecular electron migration with a first order rate constant of 1.8 X 10(4) s-1. An activation energy of the intramolecular electron transfer was calculated to be 2.8 kcal/mol in the range 4-33 degrees C.

Animals↗
PubMed1979

Regulatory interactions between mitochondrial genes. I. Genetic and biochemical characterization of some mutant types affecting apocytochrome b and cytochrome oxidase.

The region of the mtDNA containing the structural gene for apocytochrome b is called the cob or box region. There is evidence that the same region is also involved in the regulation of cytochrome oxidase. We have isolated eight mit- mutants in this region and have ordered them using petite deletion mapping. Four of these mutants appear to map outside the boxII region on the oli2-proximal end. Analysis of restriction endonuclease fragments of the mtDNA from peptides used in the deletion mapping suggests a minimum size of 3.1 x 10(3) base pairs for the whole cob region. Although none of our mutants contained any cytochrome b or cytochrome b-linked activities, polypeptides apparently related to apocytochrome b were present in some but not all mutants. Additional regulatory effects (both positive and negative) on cytochrome oxidase by virtue of control of its subunit I were also observed. In addition to these phenotypic traits, some of the mutants accumulated novel, mitochondrially translated polypeptides not seen in wild type.

Apoproteins↗
PubMed1998

Cerebral metabolism following neonatal or adult hemineodecortication in cats: effect on oxidative capacity using cytochrome oxidase histochemistry.

In order to determine the degree and extent of changes in cerebral oxidative capacity following cerebral hemineodecortication, adult cats which had undergone surgery early postnatally (mean age: 11.4 days) or during adulthood were studied using cytochrome oxidase histochemistry. A total of 18 animals were employed and 50 brain regions were quantified bilaterally using optical densitometry. Although many subcortical regions exhibiting extensive degenerative features revealed lower levels of cytochrome oxidase (C.O.) activity, this reduction was relatively unremarkable compared to intact controls. Nevertheless, it was interesting that this decrease (down to 66-89%) of normal was more pronounced in neonatal-lesioned cats, reaching significance in a number of ipsilateral thalamic nuclei, compared to adult-lesioned animals (91-100% of normal), suggesting a contribution of glial cells to the density of C.O. staining in the latter cats. Regions of the brain spared from degeneration exhibited a bilateral increase in C.O. activity which may reflect the demands for energy to support the anatomical reorganization which is prevalent in these animals. Surprisingly, such increases were more robust within spared regions of the adult-lesioned brain, reaching significance in four ipsilateral and nine contralateral areas with the density of the reaction attaining levels over 125% of control. This may indicate different demands for oxidative metabolism in the adult-lesioned cats. These results enhance our understanding of the mechanism(s) underlying the greater extent of functional sparing or recovery in cats sustaining injury to the cerebral cortex early vs. late in life. In addition, the findings complement our previous companion report on glucose metabolism supporting the concept of energy compartmentalization, which reflects the dynamic interaction between anatomical and functional changes in this age-at-lesion model of recovery.

Aging↗
PubMed1994

Structure and thermal denaturation of crystalline and noncrystalline cytochrome oxidase as studied by infrared spectroscopy.

Fourier-transform infrared spectroscopy has been applied to the study of lipid vesicle-supported two-dimensional crystals and noncrystalline preparations of beef heart cytochrome oxidase. At room temperature, no conformational differences are seen between the noncrystalline and crystalline proteins, whose conformation is shown to consist of ca. 40% alpha-helix, 20% extended structures (including beta-sheet), 17% beta-turns, and 22% open loops plus nonstructured conformations. A novel infrared approach that combines quantitative spectral band decomposition with the study of the thermal behavior of each component has been applied. The procedure allows the independent examination of temperature-induced changes in individual structural elements (alpha-helix, beta-sheet, beta-turns, and unordered). All these reflect, upon heating the protein from 20 to 80 degrees C, a major irreversible thermal event centred at 55-60 degrees C, leading to a molecular state devoid of enzyme activity but with a defined secondary structure; in addition, when the band position, percent area (integrated intensity), and bandwidth of the various amide I components are separately plotted versus temperature, each component is seen to behave in a characteristic way. Thermal denaturation in D2O buffer shows a decrease in nonstructured conformations and an increase in beta-turns without major changes in the proportion of alpha-helix. Temperature-induced changes are not the same in amorphous and crystalline structures, the latter being in general more stable toward the thermal challenge. The above data extend and confirm previous structural studies on cytochrome oxidase using cryo-electron microscopy.

Animals↗
PubMed1976

Relationship between losses in cytochrome oxidase activity and peroxidation of monosaturated phosphatidylcholines and phosphatidylethanolamines.

Incubation of inner mitochondrial membranes from rat liver in the presence of inducers of peroxidation reactions, such as ascorbate or cysteine, produced a large loss in cytochrome oxidase activity parallel to the disappearance of phosphatidylcholine and phosphatidylethanolamine molecular species, which contained a saturated and an unsaturated fatty acid. The loss in enzyme activity was unrelated to alterations in other species of these phospholipids or other ones. These results may reflect the existence of specific associations within the membrane between cytochrome oxidase and monosaturated phosphatidylcholines and/or phosphatidylethanolamines.

Animals↗
PubMed1988

Cytochemical examinations of Ca, cytochrome oxidase and succinate dehydrogenase enzymes in endometrium carcinomatous tissue after high dose progestogen treatment.

Authors investigated the effect of high dose progestogen in endometrium carcinomatous tissue on the distribution of calcium depots, as well as on the chemically detectable activity of cytochrome oxidase and succinate dehydrogenase. By means of electron microscopy no characteristic destructive effect could unequivocally be demonstrated; cytochemical examinations showed a very significant activity of cytochrome oxidase, and in the activity of succinate dehydrogenase a considerable decrease was observed. They found distributional alterations in plasma membranes, in mitochondria and in the ground cytoplasm. Changes between Ca depots are thought to have an effect on tumour cells also in a protective way, and can be regarded as compensatory phenomena.

Antineoplastic Agents↗
PubMed1995

Phylogenetic utility of the mitochondrial cytochrome oxidase gene: molecular evolution of the Drosophila buzzatii species complex.

Phylogenetic relationships among eight species of the Drosophila buzzatii species complex (D. mulleri subgroup; D. repleta species group) and D. hamatofila were determined by sequencing the mitochondrial cytochrome oxidase subunit I, II, and III genes. The species examined included members of the martensis cluster (D. martensis, D. starmeri, D. venezolana), the buzzatii cluster (D. buzzatii, D. serido, D. borborema), and the stalkeri cluster (D. stalkeri, D. richardsoni). The molecular phylogeny was found to be congruent with the chromosomal inversion phylogeny. Analyzing the cytochrome oxidase subunits separately revealed that not all the subunits seem to have the same phylogenetic information content. Parameters are discussed that might explain these differences.

Animals↗
PubMedDate not supplied

The comparative molecular study between Bombycidae and Saturniidae based on mtDNA RFLP and cytochrome oxidase I gene sequences: implication for molecular evolution.

The phylogenetic relationships between Bombyx mori and Bombyx mandarina species of Bombycidae, and Antheraea yamamai and Antheraea pernyi species of Saturniidae were investigated based on mtDNA RFLP and cytochrome oxidase I gene. The sizes of the mtDNA of all the species were estimated at approximately 16 kbp +/- 500 bp by total length of all the restricted fragments and no variation in size was recognized. Of the fourteen different restriction endonucleases used, BamHI, HindIII, PstI, EcoRI and XbaI showed RFLP. Among these, only HindIII showed RFLP between B. mori and B. mandarina. A comparative analysis of sequences was also conducted with the mitochondrial cytochrome oxidase I genes of each species. The results indicated that B. mori shared a 97%, 85% and 87% sequence identity with B. mandarina, A. yamamai and A. pernyi, respectively. B. mandarina shared a 87% and 88% sequence identity with A. yamamai and A. pernyi, respectively. A. yamamai shared 92% sequence identity with A. pernyi. The results of the phylogenetic analysis exhibited monophyly and confidence limits of more than 99% in all trees for both Bombycidae and Saturniidae.

Animals↗
PubMed1998

AZT decreases rat myocardial cytochrome oxidase activity and increases beta-myosin heavy chain content.

AZT, a widely-utilized drug for the treatment of HIV infection, inhibits the polymerase responsible for mitochondrial DNA replication (mtDNA). The aim of this study was to assess myocardial alterations caused by this action. Ventricular muscle from rats treated for > or = 35 days with 1 mg/ml of AZT in their drinking water was analysed for cytochrome oxidase activity and the content of mRNAs for the nuclear-encoded cytochrome oxidase (COX) subunit VIc and the mitochondrial-encoded COX subunit III. In addition contractile protein expression was assessed by examining mRNA levels for alpha- and beta-myosin heavy chains (MHC). Changes in MHC mRNA levels were correlated with changes in alpha- and beta-MHC proteins and changes in myofibrillar ATPase activity. Results show that AZT caused a reduction in COX activity, COX subunit III mRNA, and mtDNA levels. There was no decrease in the COX subunit VIc mRNA. MHC expression was altered such that the relative content of beta-MHC protein and mRNA were increased. Accumulation of beta-MHC was reflected in the reduction of myofibrillar ATPase activity at pCa values of 5.875 and 6.125. These data demonstrate that AZT induces a reorganization of cardiac gene expression indicative of changes in cardiac contractile properties. The observed decreases in mtDNA levels along with mRNA for a mitochondrial-encoded protein and COX activity is consistent with the postulated mechanism whereby AZT induces a myopathy by diminishing mtDNA replication.

Animals↗
PubMed1977

Acid hydrolase and cytochrome oxidase activities in nitrosourea induced tumors of the nervous system.

Nitrosourea induced tumors of the nervous system in rats have proven useful for biochemical studies combined with morphological approaches. The pattern of enzyme activities for acid hydrolases and cytochrome oxidase resemble those previously observed in spontaneous nervous system tumors of man. The activities of 4 acid hydrolases were generally high in the gliomas. This could not be attributed solely to zones of regression or necrosis but was a general characteristic of the neoplasms. The activities were predominantly particulate and most likely lysosomal in localization. In schwannomas a similar increase in hydrolases was found in comparison with normal neural tissues but aryl-sulfatase was not increased. Cytochrome oxidase activities were markedly reduced in all tumors studied. The proportionate reduction with respect to normal brain was comparable to that noted in man. No differences were found with respect to fairly well differentiated gliomas.

Animals↗
PubMed1986

Pseudomonas aeruginosa cytochrome oxidase. Product inhibition by low thermodynamic driving force.

The steady-state kinetics of Pseudomonas aeruginosa cytochrome oxidase were studied. Reduced cytochrome c551 and azurin from the same bacteria were used as the electron-donating substrates, while dioxygen served as the electron acceptor. Oxidized cytochrome c551 and azurin exhibited product inhibition of the reaction. However, apo-azurin and azurin derivatives in which the copper was substituted by the redox-inert ions Ni2+, Co2+, Cd2+ and Zn2+, did not show any effect on the kinetics. These observations implied that complex formation between the substrates or the products and the enzyme is not a rate-limiting step and is not the cause for product inhibition. The integrated rate law for a reaction scheme in which we assumed that complex formation was not rate limiting was fitted to the complete reaction traces. The results suggested that it is the low thermodynamic driving force, expressed in the small differences in redox potential between the substrates and heme c of the enzyme, which cause the observed product inhibition.

Azurin↗
PubMed1987

Cytochrome oxidase activity of postsurgical bullous keratopathy endothelium.

Proper corneal hydration is normally maintained by a pump-leak mechanism located on the lateral cell membranes of the endothelium (1,2). When endothelial cells become sufficiently dysfunctional in response to trauma, the cornea becomes irreversibly edematous and opaque. Previous studies in our laboratory have shown that mitochondrial cytochrome oxidase (CO) activity, an enzyme important in respiratory activities, is correlated with endothelial cell functional activity in corneas with Fuchs' endothelial dystrophy. In this study we investigated cytochrome oxidase activity in corneas with postsurgical bullous keratopathy. Corneas with aphakic and pseudophakic bullous keratopathy (ABK, PBK) were incubated in diaminobenzidine-cytochrome C media. Results showed that the staining pattern of ABK and PBK corneas was uniformly low compared to keratoconus corneas, and in contrast to previous studies on Fuchs' dystrophy corneas which demonstrated a regional staining pattern. This suggests that CO staining patterns correlate with functional activity and may be a useful technique to detect dysfunctional cells in various disease categories.

Corneal Diseases↗
PubMed2006

Characterization of two cytochrome oxidase operons in the marine cyanobacterium Synechococcus sp. PCC 7002: inactivation of ctaDI affects the PS I:PS II ratio.

Cyanobacteria have versatile electron transfer pathways and many of the proteins involved are functional in both respiratory and photosynthetic electron transport. Examples of such proteins include the cytochrome b (6) f complex, NADH dehydrogenase and cytochrome oxidase complexes. In this study we have cloned and sequenced two gene clusters from the marine cyanobacterium Synechococcus sp. PCC 7002 that potentially encode heme-copper cytochrome oxidases. The ctaCIDIEI and ctaCIIDIIEII gene clusters are most similar to two related gene clusters found in the freshwater cyanobacterial strain Synechocystis sp. PCC 6803. Unlike Synechocystis sp. PCC 6803, Synechococcus sp. PCC 7002 does not have a cydAB-like gene cluster which encodes a quinol oxidase. The ctaCIDIEI and ctaCIIDIIEII gene clusters were transcribed polycistronically, although the levels of transcripts for the ctaCIIDIIEII gene cluster were lower than those of the ctaCIDIEI gene cluster. The ctaDI and ctaDII coding sequences were interrupted by interposon mutagenesis and full segregants were isolated and characterized for both single and double mutants. Growth rates, chlorophyll and carotenoid contents, oxygen consumption and oxygen evolution were examined in the wild type and mutant strains. Differences between the wild type and mutant strains observed in 77 K fluorescence spectra and in pulse-amplified modulated (PAM) fluorescence studies suggest that the cyanobacterial oxidases play a role in photoinhibition and high light tolerance in Synechococcus sp. PCC 7002.

Amino Acid Sequence↗
PubMed2001

Sequence variation in the cytochrome oxidase I, internal transcribed spacer 1, and Ts14 diagnostic antigen sequences of Taenia solium isolates from South and Central America, India, and Asia.

We examined the genetic variability in the pig-human tapeworm, Taenia solium, by sequencing the genes for cytochrome oxidase I, internal transcribed spacer 1, and a diagnostic antigen, Ts14, from individual cysts isolated from Peru, Colombia, Mexico, India, China, and the Philippines. For these genes, the rate of nucleotide variation was minimal. Isolates from these countries can be distinguished based on one to eight nucleotide differences in the 396 nucleotide cytochrome oxidase I (COI) sequence. However, all of the 15 isolates from within Peru had identical COI sequences. The Ts14 sequences from India and China were identical and differed from the Peru sequence by three nucleotides in 333. These data indicate that there is minimal genetic variability within the species T. solium. Minimal variability was also seen in the ITS1 sequence, but this variation was observed within the individual. Twenty-two cloned sequences from six isolates sorted into 13 unique sequences. The variability observed within the sequences from individual cysts was as great as the variability between the isolates.

Animals↗
PubMed2004

Solution structure of Cox11, a novel type of beta-immunoglobulin-like fold involved in CuB site formation of cytochrome c oxidase.

Cytochrome c oxidase assembly process involves many accessory proteins including Cox11, which is a copper-binding protein required for Cu incorporation into the Cu(B) site of cytochrome c oxidase. In a genome wide search, a number of Cox11 homologs are found in all of the eukaryotes with complete genomes and in several Gram-negative bacteria. All of them possess a highly homologous soluble domain and contain an N-terminal fragment that anchors the protein to the membrane. An anchor-free construct of 164 amino acids was obtained from Sinorhizobium meliloti, and the first structure of this class of proteins is reported here. The apoform has an immunoglobulin-like fold with a novel type of beta-strand organization. The copper binding motif composed of two highly conserved cysteines is located on one side of the beta-barrel structure. The apoprotein is monomeric in the presence of dithiothreitol, whereas it dimerizes in the absence of the reductant. When copper(I) binds, NMR and extended x-ray absorption fine structure (EXAFS) data indicate a dimeric protein state with two thiolates bridging two copper(I) ions. The present results advance the knowledge on the poorly understood molecular aspects of cytochrome c oxidase assembly.

Amino Acid Motifs↗