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)

The effects of thyroid hormone on nuclear-encoded mitochondrial inner membrane proteins were investigated by in vitro translation of the endogenous mRNA present in a postmitochondrial fraction from the livers of rats treated in vivo with hormone. The levels of the mRNAs were estimated by quantitative immunoabsorption of the translation mixture. Total protein synthesis was increased 2.6-fold after 4 days of in vivo hormone treatment, but only 10-15% of the polypeptides were dramatically altered (greater than 5-fold). Among the most highly elevated were cytochrome c1 (greater than 10-fold increase) and the Rieske iron-sulfur protein of the cytochrome bc1 complex. Other inner membrane proteins (core protein 1, beta subunit of F1 ATPase, subunit IV of cytochrome oxidase, 3-hydroxybutyrate dehydrogenase) and non-mitochondrial proteins (rat serum albumin, beta 2-microglobulin) were not altered significantly by hormone treatment. Cytochrome c1 and the Rieske protein increased after 12 h of hormone treatment, a relatively early response in mammalian mitochondrial biogenesis. The possible significance of this response for the regulation of mitochondrial synthesis and assembly is discussed.
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PMID:Thyroid hormone regulation of nuclear-encoded mitochondrial inner membrane polypeptides of the liver. 277 68

Several inner membrane proteins from rat liver mitochondria have been translated for the first time in rabbit reticulocyte lysates. These include the Rieske iron-sulfur protein, cytochrome c1 and core protein I of the cytochrome bc1 complex, the alpha and beta subunits of F1 ATPase, and subunit IV of cytochrome oxidase. All were translated from free polysomes as larger-molecular-mass precursors, and were processed to their mature forms by isolated liver mitochondria or by the isolated mitochondrial matrix fraction. In vitro processing, catalyzed by the isolated matrix fraction, is inhibited by rhodamine 6G. The latter is a fluorescent probe, which accumulates specifically in mitochondria of whole cells and which is used extensively to visualize mitochondrial morphology. The concentration of rhodamine 6G required for inhibition in vitro is similar to that of o-phenanthroline. Rhodamine 6G inhibits matrix-catalyzed processing of all precursors tested, indicating that the mechanism of inhibition is common for a variety of functionally unrelated precursors. The novel action of rhodamine 6G reported here can form the basis for its inhibition of precursor processing in intact hepatoma cells [Kolarov, J. & Nelson, B.D. (1984) Eur. J. Biochem. 144, 387-392].
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PMID:Rhodamine 6G inhibits the matrix-catalyzed processing of precursors of rat-liver mitochondrial proteins. 286 95

One polypeptide subunit of cytochrome c oxidase (EC 1.9.3.1) and two subunits of the ATPase/ATP synthase (EC 3.6.1.34) in mitochondria of Neurospora crassa are covalently modified with a derivative of pantothenic acid. In asexual spores of a pantothenate auxotroph of Neurospora, deprivation of pantothenic acid blocked the increase of the specific activities of cytochrome c oxidase and the ATPase above the basal activities in the dormant spores. Under cellular panthothenate deprivation, all the subunit peptides of these two enzymes apparently were synthesized and accumulated in the mitochondria, but these subunits were not assembled into normal complexes, and 55Fe-labeled heme a was incorporated into immunoprecipitable cytochrome c oxidase to a very low extent. In pantothenate-supplemented cells, the pantothenate derivative apparently is attached to the free unassembled subunits and appears not to be present in the assembled enzymes. It is likely that cellular deprivation of pantothenate, resulting in failure to modify the three subunit peptides, causes an interruption of the assembly pathway of cytochrome c oxidase and the ATPase/ATP synthase.
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PMID:Pantothenate is required in Neurospora crassa for assembly of subunit peptides of cytochrome c oxidase and ATPase/ATP synthase. 287 72

Two multisubunit enzymes of the inner mitochondrial membrane, cytochrome oxidase and the H+-ATPase may be transferred into highly apolar solvents as protein-lipid complexes. At 70 degrees C and an initial water concentration of 13 microliters per ml organic solvent (toluene), the half-life of the ATPase was approx. 11 h, whereas that of cytochrome oxidase was about 100 s. Thermostability of cytochrome oxidase could be increased more than 100-times by decreasing the water concentration to 3 microliters per ml toluene. At this latter concentration of water the half-life of the ATPase at 90, 80 and 70 degrees C was 5, 48 and 96 h, respectively.
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PMID:Thermostability of membrane systems in organic solvents. 287 58

bI4 maturase, encoded by the fourth intron of the yeast mitochondrial cytochrome b gene, controls the splicing of both the fourth intron of the cytochrome b gene and the fourth intron of the gene encoding subunit I of cytochrome oxidase. By fusing the encoding presequence of subunit 9 of the Neurospora ATPase to a restriction fragment containing the bI4 maturase coding sequence, we have constructed a hybrid gene that can be translated on yeast cytosolic ribosomes. The resulting protein is imported into mitochondria, which was revealed by its ability to restore to respiratory competence a yeast mutant defective in the bI4 maturase. Moreover, a protein reacting with antimaturase antibodies was detected in the mitochondria of the transformed cells; this imported maturase functioned similarly to the endogenous maturase.
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PMID:A mitochondrial RNA maturase gene transferred to the yeast nucleus can control mitochondrial mRNA splicing. 287 97

Subunit 8 of yeast mitochondrial F1F0-ATPase is a proteolipid made on mitochondrial ribosomes and inserted directly into the inner membrane for assembly with the other F0 membrane-sector components. We have investigated the possibility of expressing this extremely hydrophobic, mitochondrially encoded protein outside the organelle and directing its import back into mitochondria using a suitable N-terminal targeting presequence. This report describes the successful import in vitro of ATPase subunit 8 proteolipid into yeast mitochondria when fused to the targeting sequence derived from the precursor of Neurospora crassa ATPase subunit 9. The predicted cleavage site of matrix protease was correctly recognized in the fusion protein. A targeting sequence from the precursor of yeast cytochrome oxidase subunit VI was unable to direct the subunit 8 proteolipid into mitochondria. The proteolipid subunit 8 exhibited a strong tendency to embed itself in mitochondrial membranes, which interfered with its ability to be properly imported when part of a synthetic precursor.
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PMID:Yeast mitochondrial ATPase subunit 8, normally a mitochondrial gene product, expressed in vitro and imported back into the organelle. 288 82

It is possible to prepare liposomal vesicles by solubilization of total bacterial membranes with n-heptyl beta-D-thioglucoside followed by reconstitution into proteoliposomes by a freeze-thaw-sonication procedure with soybean phospholipids. The resulting proteoliposomes from total membrane fraction of sufficiently aerated cells of the thermophilic bacterium PS3 containing cytochrome aa3 showed a reasonable H+ pumping activity upon addition of reduced cytochrome c. On the other hand, the proteoliposomes reconstituted from air-limited PS3 cells containing cytochrome o and those from Nitrobacter agilis cells containing cytochrome aa3 did not show H+ pumping upon addition of reduced cytochrome c, although the vesicles showed "respiratory control"; 3-4-fold stimulation of oxygen consumption took place upon addition of an uncoupler. In proteoliposomes prepared from PS3 membranes by this method, H+-translocating ATPase (F0 X F1) was successfully reconstituted as well, suggesting that this method has wide applicability for investigation of enzymes catalyzing transmembrane processes.
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PMID:Measurement of proton pump activity of the thermophilic bacterium PS3 and Nitrobacter agilis at the cytochrome oxidase level using total membrane and heptyl thioglucoside. 288 79

Vesicles from yeast plasma membrane were prepared according to Franzusoff and Cirillo [1983) J. Biol. Chem. 258, 3608), with slight modifications. When Mg-ATP was added, this preparation was able to generate a membrane potential, that was sensitive to inhibitors of the yeast H+-ATPase and uncouplers, and could be decreased by the addition of permeant anions, as measured by the fluorescence changes of the dye oxonol V. The addition of ATP could also generate a pH gradient, detectable by the fluorescence changes of the monitor aminochloromethoxyacridine. This gradient was sensitive to inhibitors of ATPase and uncouplers, and could be increased by the addition of permeant anions to the incubation mixture. When the vesicles were loaded with KCl, an increased rate of K+ efflux was produced upon the addition of ATP. Cytochrome oxidase from bovine heart could be reconstituted into the vesicles and was shown to generate a membrane potential difference, negative inside, evidenced by the fluorescence quenching of the cyanide dipropylthiacarbocyanine and the uptake of tetraphenylphosphonium. Besides, in these vesicles, K+ and Rb+, but not Na+ or NH+4 could decrease the quenching of fluorescence and the uptake of tetraphenylphosphonium produced when the electron-donor system was present. In the vesicles in which cytochrome oxidase was incorporated, upon the addition of cytochrome c and ascorbate, the uptake of 86Rb+ could be demonstrated also. This uptake was found to be saturable and inhibited by K+, and to a lesser degree by Na+. The results obtained indicate that these vesicles are reasonably sealed and capable of generating and maintaining a membrane potential. The membrane potential could be used to drive ions across the membrane of the vesicles, indicating the presence and functionality of the monovalent cation carrier. The vesicles, in general terms seem to be suitable for studying transport of ions and metabolites in yeast.
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PMID:Electrochemical potential and ion transport in vesicles of yeast plasma membrane. 288 94

To evaluate the participation of proteins derived from mitochondrial genes in the adaptive response of skeletal muscle to increased contractile activity, we administered chloramphenicol (CAP; 200-1,000 mg.kg-1.day-1), an inhibitor of translation from mitochondrial ribosomes, to adult rabbits undergoing electrical stimulation of the tibialis anterior muscle of one hind limb. In unmedicated animals, 10 days of electrical stimulation increased maximum velocity (Vmax) of cytochrome oxidase and citrate synthase by 214 +/- 17 and 201 +/- 16% (P less than 0.01). In a dose-dependent manner, CAP abolished activity-induced increases in cytochrome oxidase Vmax, suggesting that augmented mitochondrial protein synthesis is necessary for the adaptive response of enzymes that require protein subunits encoded by mitochondrial genes. However, CAP failed to inhibit activity-induced changes in Vmax of enzymes derived exclusively from nuclear genes (citrate synthase and aldolase). CAP also failed to inhibit activity-induced increases in mRNA transcribed from the nuclear genes encoding beta-F1 ATPase or myoglobin, or from the mitochondrial genes encoding 12S rRNA, 16S rRNA, or cytochrome b. These latter findings suggest that mitochondrial translation products do not participate in pretranslational regulation of these nuclear or mitochondrial genes in response to changes in contractile activity of skeletal muscle.
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PMID:Effects of inhibition of mitochondrial protein synthesis in skeletal muscle. 289 13

A fine restriction map of the linear mitochondrial DNA of Tetrahymena pyriformis strain ST is presented. 1. Based on agarose gel electrophoresis data together with limited nucleotide sequences available on some restriction fragments, we estimate the actual size of this genome to be about 55,000 base pairs. 2. Seven tRNA gene locations have been assigned, which are scattered along the genome length. Six of these locations encode the genes for tRNA(phe), tRNA(his), tRNA(trp), and tRNA(glu), and the duplicate tRNA(tyr) genes which are located at the inverted terminal repeat segments. The tRNA gene(s) encoded in one location has not been identified. We have not yet found the tRNA(leu) and tRNA(met) genes, which were previously shown to be encoded in the genome (Chiu et al. 1974; Suyama 1982). 3. We have mapped the 14S rRNA gene by sequencing the 170 bp segment of EcoRI fragment 8 and by aligning its sequence with E. coli 16S rRNA. From our recent complete sequence data the gene size was found to be about 1,650 bp, which is unexpectedly large for the 14S rRNA which has an estimated size of 1,300 bp. The 14S rRNA is probably a cleavage product of the larger primary transcript of which 200-300 bases of the 5' end are missing. 4. The duplicate copies of the 21S rRNA gene at the terminal duplication inversion segments were analyzed. ClaI fragment 7 (1,500 bp) corresponds in sequence from base position 850 to 2,390 of the 20S rRNA gene of Paramecium mitochondrial DNA (Seilhamer et al. 1984b). The 21S gene is approximately 2,500 bp long. The presence of some restriction site polymorphism is apparent in this segment. 5. Each of the 21S gene copies precedes the tRNA(tyr) gene, but the space flanking one tRNA(tyr) gene differs in size and restriction sites from the space flanking another tRNA(tyr) gene. Thus, this space corresponds to the segment of an imperfect match in the terminal duplication inversion of Goldbach et al. (1978a). 6. Saccharomyces cerevisiae mitochondrial probes including Cob, ATPase VI and IX, and cytochrome oxidase I gene sequences, 21S and 15S rRNAs, and mouse mitochondrial DNA showed no significant hybridization with any restriction fragments of Tetrahymena mitochondrial DNA. The results are in accordance with an extensive sequence divergence previously found in the Tetrahymena mitochondrial genome (Goldbach et al. 1977).
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PMID:A fine restriction map of the linear mitochondrial DNA of Tetrahymena pyriformis: genome size, map locations of rRNA and tRNA genes, terminal inversion repeat, and restriction site polymorphism. 289 50


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