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Query: UNIPROT:P06889 (Mol)
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Hippocampal CA1 neurons are the most vulnerable to transient cerebral ischemia. However, the mechanism has not been fully understood. The level of mRNA for cytochrome c oxidase subunit I (COX-I), which is encoded by mitochondrial DNA (mtDNA), progressively decreased in the hippocampal CA1 neurons of gerbils from 1 to 3 h of the reperfusion after 3.5 min of transient forebrain ischemia, and completely disappeared at 7 days. The activity of cytochrome c oxidase (COX) protein also showed the early decrease in the CA1 cells, and was followed by the reduction of the level of COX-I DNA after 2 days. However, the activity of succinic dehydrogenase (SDH), a mitochondrial enzyme that is encoded by nuclear DNA, maintained normal activity until 1 day in the CA1 cells, and significantly decreased at 7 days. These results suggest that disturbance of mitochondrial DNA expression occurred in the CA1 neurons at the early stage of reperfusion, and was aggravated in the course of time. The disturbance could cause progressive failure of energy production of the cells that eventually results in the neuronal cell death.
Brain Res Mol Brain Res 1993 Jul
PMID:Disturbance of a mitochondrial DNA expression in gerbil hippocampus after transient forebrain ischemia. 839 30

Cytochrome c oxidase was isolated from livers and hearts of sheep, dog and rabbit, and the polypeptide composition was analyzed by two different SDS-PAGE separation systems. The gels were blotted on PVDF-membranes and the N-terminal amino acid sequences of the tissue-specific subunits VIa, VIIa and VIII were determined in a protein sequencer. Except for subunit VIIa from rat, subunits VIa and VIIa from all investigated mammals are tissue-specific expressed in liver and heart. In contrast, subunit VIII is clearly different in liver and heart of bovine, dog and rat, but identical in liver and heart of human (liver-type), sheep, rabbit and also in rainbow trout (heart-type). The data suggest a strong species-specific variation of the regulatory properties of cytochrome c oxidase in different tissues.
Comp Biochem Physiol B Biochem Mol Biol 1995 Nov
PMID:Species-specific expression of cytochrome c oxidase isozymes. 852 22

Defects of the respiratory chain carrying out oxidative phosphorylation (OXPHOS) are the biochemical hallmark of human mitochondrial disorders. Faulty OXPHOS can be due to mutations in either nuclear or mitochondrial genes, that are involved in the synthesis of individual respiratory subunits or in their post-translational control. The most common mitochondrial disorder of infancy and childhood is Leigh's syndrome, a severe encephalopathy, often associated with a defect of cytochrome c oxidase (COX). In order to demonstrate which genome is primarily involved in COX-deficient (COX(-))-Leigh's syndrome, we generated two lines of transmitochondrial cybrids. The first was obtained by fusing nuclear DNA-less cytoplasts derived from normal fibroblasts, with mitochondrial DNA-less (rho degree) transformant fibroblasts derived from a patient with COX(-))-Leigh's syndrome. The second cybrid line was obtained by fusing rho degree cells derived from 143B.TK- human osteosarcoma cells, with cytoplasts derived from the same patient. The first cybrid line showed a specific and severe COX(-) phenotype, while in the second all the respiratory chain complexes, including COX, were normal. These results indicate that the COX defect in our patient is due to a mutation of a nuclear gene. The use of cybrids obtained from 'customized', patient-derived rho degree cells can have wide applications in the identification of respiratory chain defects originated by nuclear DNA-encoded mutations, and in the study of nuclear DNA-mitochondrial DNA interactions.
Hum Mol Genet 1995 Nov
PMID:Nuclear DNA origin of cytochrome c oxidase deficiency in Leigh's syndrome: genetic evidence based on patient's-derived rho degrees transformants. 858 77

We previously demonstrated that feeding rats the Steenbock and Black rickets-inducing diet produces remarkable changes in the metabolic pattern of intestinal mucosa, kidney, liver, cerebral cortex and heart. We have now determined the levels of calcium, phosphorus and citrate in cerebral cortex and the activity of some enzymes in synaptosomes and cerebral cortex mitochondria of three rat groups: control (Group A), fed a vitamin D-deficient diet (Group B), fed a vitamin D-deficient diet and treated with 1,25-dihydroxyvitamin D3 (Group C). While calcium content increased in Groups B and C, phosphorus concentration increased only in Group C and citrate in Group B in comparison with control. The increase in acetylcholinesterase and citrate synthase registered in Group B was restored to control values by 1,25-dihydroxyvitamin D3 treatment, while, neither the decrease in cytochrome c oxidase, nor the increase in glucose-6-phosphate dehydrogenase, acid phosphatase and NADP+(-)isocitrate dehydrogenase observed in Group B were corrected by 1,25-dihydroxyvitamin D3 supply. Acyl phosphatase showed a remarkable increase in consequence of 1,25-dihydroxyvitamin D3 administration.
Biochem Mol Biol Int 1995 Nov
PMID:Vitamin D--related modification of enzyme activities in synaptosomes and mitochondria isolated from rat cerebral cortex. 862 85

We have investigated the expression of a continuous open reading frame (ORF) present in the mitochondrial genome of Acanthamoeba castellanii and specifying the two largest subunits (COX1 and COX2) of the cytochrome c oxidase complex. Northern hybridization and primer extension analysis demonstrated that this ORF (cox1/2, 873 codons) is transcribed as part of a 4.7 kb RNA that also includes the upstream small subunit rRNA sequence. Between the cox1 and cox2 portions of the transcript, RNA sequence exactly matches gene sequence, excluding the possibility that a standard cox1 termination codon is created by post-transcriptional RNA processing or editing. Western analysis revealed an A. castellanii COX2 protein with a mobility matching that of mature COX2 from yeast (Saccharomyces cerevisiae) mitochondria. These observations indicate that although A. castellanii COX1 and COX2 are apparently translated from the same ORF, they do not exist in mature form as a COX1-COX2 "fusion" protein. Whereas translation of COX2 could potentially be initiated from an internal AUG codon in the cox1/2 ORF, COX1 must be generated either through an unusual translation termination mechanism acting between the cox1 and cox2 coding regions of the cox1/2 mRNA, or by co-translational or post-translational proteolytic processing of a translation product whose synthesis continues into the cox2 coding region. Because the cox2 nucleotide sequence predicts a COX2 protein considerably larger than that observed by Western analysis, A. castellanii COX2 may undergo additional post-translational processing to its final form.
J Mol Biol 1996 Apr 19
PMID:Expression of a continuous open reading frame encoding subunits 1 and 2 of cytochrome c oxidase in the mitochondrial DNA of Acanthamoeba castellanii. 863 65

Morphology and respiratory function were studied in situ and in the isolated mitochondria of Paragonimus ohirai. Two types of parenchymal cells (i.e., Pc1 and Pc2 cells), whose mitochondria differ in terms of morphology and staining for cytochrome c oxidase activity, were found in fluke tissues. Enzymatic and spectrophotometric analyses of the isolated mitochondria showed that fluke mitochondria possess both aerobic and anaerobic respiratory chains. These results suggest that there are two mitochondrial populations in fluke parenchymal cells, one possessing an aerobic respiratory chain and the other an anaerobic respiratory chain.
Comp Biochem Physiol B Biochem Mol Biol 1996 Feb
PMID:Two types of parenchymal cells in the lung fluke Paragonimus ohirai (Digenea: Troglotrematidae) characterized by the cytochemistry of their mitochondria. 865 91

Utilizing a recently developed novel fluorescence technique [Wall et al. (1995) Mol. Membr. Biol. 12, 183-192], it is shown that the interactions of p25, the leader peptide of subunit IV of cytochrome c oxidase, with phospholipid membranes can be identified in real time. p25 is observed to bind following stopped-flow mixing of the peptide with phospholipid membranes with rate constants up to about 700 s-1 and then insert into the membrane with rate constants on the order of 0.4 s-1. Comparison of these processes with similarly time-resolved experiments performed with a stopped-flow CD spectrometer revealed that p25 does not become alpha-helical upon binding to the membrane. Following membrane insertion, however, p25 was observed to adopt an alpha-helical configuration. The temperature dependency of these processes was then found to yield activation energies for the respective components of the p25-membrane interaction.
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PMID:Time resolution of binding and membrane insertion of a mitochondrial signal peptide: correlation with structural changes and evidence for cooperativity. 871 86

In Paracoccus denitrificans the aa3-type cytochrome c oxidase and the bb3-type quinol oxidase have previously been characterized in detail, both biochemically and genetically. Here we report on the isolation of a genomic locus that harbours the gene cluster ccoNOOP, and demonstrate that it encodes an alternative cbb3-type cytochrome c oxidase. This oxidase has previously been shown to be specifically induced at low oxygen tensions, suggesting that its expression is controlled by an oxygen-sensing mechanism. This view is corroborated by the observation that the ccoNOOP gene cluster is preceded by a gene that encodes an FNR homologue and that its promoter region contains an FNR-binding motif. Biochemical and physiological analyses of a set of oxidase mutants revealed that, at least under the conditions tested, cytochromes aa3, bb3 and cbb3 make up the complete set of terminal oxidases in P. denitrificans. Proton-translocation measurements of these oxidase mutants indicate that all three oxidase types have the capacity to pump protons. Previously, however, we have reported decreased H+/e- coupling efficiencies of the cbb3-type oxidase under certain conditions. Sequence alignment suggests that many residues that have been proposed to constitute the chemical and pumped proton channels in cytochrome aa3 (and probably also in cytochrome bb3) are not conserved in cytochrome cbb3. It is concluded that the design of the proton pump in cytochrome cbb3 differs significantly from that in the other oxidase types.
Mol Microbiol 1996 Jun
PMID:Structural and functional analysis of aa3-type and cbb3-type cytochrome c oxidases of Paracoccus denitrificans reveals significant differences in proton-pump design. 880 76

Embryos of the brine shrimp Artemia franciscana are able to withstand long bouts of environmental anoxia by entering a quiescent state during which metabolism is greatly depressed. Recent evidence supports a global arrest of protein synthesis during quiescence. In this study we measured the amounts of mRNA for a mitochondrial-encoded subunit of cytochrome c oxidase (COX I) and for nuclear-encoded actin during aerobic development, anaerobiosis, and aerobic acidosis (artificial quiescence imposed by intracellular acidification under aerobic conditions). The levels of both COX I and actin transcripts increased significantly during aerobic development. COX I mRNA levels were tightly correlated with previous measures of COX catalytic activity, which suggests that COX synthesis could be regulated by message concentration during aerobic development. The ontogenetic increase for these mRNAs was blocked by anoxia and aerobic acidosis. Importantly, the levels of COX I and actin mRNA did not decline appreciably during the 6 h bouts of quiescence, even though protein synthesis is acutely arrested by these same treatments. Thus, the constancy of mRNA levels during quiescence indicate that reduced protein synthesis is not caused by message limitation, but rather, is likely controlled at the translational level. One advantage of this regulatory mechanism is the conservation of mRNA molecules during quiescence, which would potentially favor a quick resumption of translation as soon as oxygen is returned to the embryos. Finally, because anoxia and aerobic acidosis are both characterized by acidic intracellular pH, the reduction in pH may serve, directly or indirectly, as one signal regulating levels of mRNA in this embryo during quiescence.
Mol Cell Biochem 1996 May 24
PMID:Profiles of nuclear and mitochondrial encoded mRNAs in developing and quiescent embryos of Artemia franciscana. 881 76

Contrary to previous reports, the functional and spectral properties of "monomeric" shark cytochrome c oxidases are not entirely similar to those of the "dimeric" beef enzyme. Most significantly, unlike the behavior of beef oxidase, the fully oxidized shark enzyme is not reducible by carbon monoxide. Also, preparations of the shark enzyme, isolated at pH 7.8-8.0, lead to more than 60% of the sample always being obtained in a resting form, whereas similarly prepared beef oxidase is very often obtained, both by ourselves and others, exclusively in the pulsed form. Although the electronic absorption, magnetic circular dichroism and electron paramagnetic resonance (EPR) spectra of cytochrome c oxidase obtained from several shark species are similar to those of the beef enzyme, there are some significant differences. In particular, the Soret maximum is at 422 nm in the case of the fully oxidized resting shark oxidases at physiological pH and not 418 nm as commonly found for the beef enzyme. Moreover, the resting shark oxidases do not necessarily exhibit a "g = 12" signal in their EPR spectra. The turnover numbers of recent preparations of the shark enzyme are higher than previously reported and, interestingly, do not differ within experimental uncertainty from those documented for several beef isoenzymes assayed under comparable conditions.
Comp Biochem Physiol B Biochem Mol Biol 1996 Aug
PMID:A carbon monoxide irreducible form of cytochrome c oxidase and other unusual properties of the "monomeric" shark enzyme. 884 May 11


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