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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)

Seven protein subunits of cytochrome c oxidase from bovine heart were isolated by gel filtration in the presence of sodium dodecyl sulphate (subunits I, II and III) and guanidine hydrochloride (subunits V, VI and VII), and ion-exchange chromatography in 6 M urea (subunit IV) after the enzyme had been dissociated in 6 M guanidine hydrochloride. When analysed by highly cross-linked sodium dodecyl sulphate/polyacrylamide gel electrophoresis in the presence of urea, the apparent molecular weights were = I, 36700; II, 24300; III, 20400; IV, 17300; V, 12300; VI, 8700: and VII, 5100. Monospecific rabbit antisera were obtained against subunits I, IV, V, VI and VII and a mixture of subunits II and III. These subunit-specific antisera with the exception of anti-I serum all cross-reacted with the detergent-solubilized native oxidase. Enzymatic studies on purified oxidase indicated that immunoglobulins against subunits II + III, IV, V, VI and VII respectively caused 25, 65, 20, 30 and 25% inhibition while anti-I immunoglobulin did not inhibit the activity. The subunit-specific antisera were used to examine the arrangements of the subunits in the membrane. Enzymatic studies using bovine heart mitochondria and rat liver mitochondrial digitonin particles showed that anti-(II + III) serum, anti-V serum and anti-VII serum all inhibited the oxidase activity while the other antisera did not. On the other hand, results of using 125I-labelled immunoglobulins showed that anti-IV, anti-V and anti-VII sera were bound to the surface of inverted vesicles (matrix side) while all other antisera were not. These results indicate that cytochrome oxidase subunits II and III are situated on the outer surface, and subunit IV is exclusively on the matrix surface while subunits V and VII are exposed on both surfaces of the mitochondrial membrane. Subunits I and VI are buried within the membrane, not exposed on either side.
Eur J Biochem 1978 Sep 01
PMID:Immunological studies on cytochrome c oxidase: arrangements of protein subunits in the solubilized and membrane-bound enzyme. 21 67

A novel immunological procedure has been applied for the isolation of precursors of cytochrome oxidase. It involves antibodies to individual subunits of the oxidase and protein A from Staphylococcus aureus linked to a Sepharose support. Unassembled (free) 'subunits' as well as a labile complex containing five polypeptide components of the oxidase were isolated from mitochondrial extracts by this technique. The procedure is superior to the previously used double-immuno-precipitation method, because of its quantitative nature, its sensitivity, rapidity and versatility. Thus, sequential titrations of precursor proteins by addition of various subunit-specific immuno-globulins to an individual extract become feasible. Furthermore, the technique is suitable for the isolation of precursors on a large scale. To avoid contamination of the polypeptide preparations with immunoglobulin, the antibodies were covalently coupled to protein A, which had been previously linked to Sepharose. A radioactive preparation of unassembled subunit 1 of cytochrome oxidase was isolated by such a modified support and its cyanogen-bromide-cleavage products were compared to those of subunit 1 obtained from the assembled enzyme.
Eur J Biochem 1978 Sep 15
PMID:Isolation of precursors of cytochrome oxidase from Neurospora crassa: application of subunit-specific antibodies and protein A from Staphylococcus aureus. 21 73

Intracellular amastigotes of Leishmania donovani obtained from spleens of infected hamsters were studied by means of the diaminobenzidine technique for the presence of cytochromes and the activities of cytochrome oxidase and peroxidase. In the absence of H2O2, the oxidation of DAB, evidenced by electron-dense deposits localized on the cristae, inclusions, and enveloping membranes of the mitochondria and kinetoplast, revealed the activity of the cytochrome oxidase and the presence of the cytochromes. The increased deposition of DAB oxidation especially on the enveloping membranes in the presence of H2O2 suggests the activity of a peroxidase, probably cytochrome c peroxidase.
Tropenmed Parasitol 1978 Sep
PMID:Leishmania donovani: ultrastructural localization of diaminobenzidine reactivity in the amastigotes. 21 7

Lipid-depleted cytochrome c oxidase (EC 1.9.3.1) containing less than 20 microgram lipids per milligram protein was reconstituted with pure phospholipids of well-defined chemical structure and fatty acid composition without using detergents and (or) sonication. For the maximal restoration of electron transport activity, lipid-depleted cytochrome c oxidase required acidic phospholipds such as phosphatidylglycerol or phosphatidylserine or lysophospholipids such as lysophosphatidylcholine or lysophosphatidic acid, but no specific phospholipid fatty acid composition was necessary. The organization of the lipid environment of the reconstituted cytochrome c oxidase, having a well-defined lipid composition, morphology, and a high specific activity, was examined by electron spin resonance spectroscopy using 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl (16-doxyl stearic acid) and 16-doxyl stearic acid - containing phosphatidylglycerol. The presence of boundary lipid was established in both lamellar and micellar organizations of reconstituted cytochrome c oxidase and was not necessarily related to the enzymatic activity of the complex. Our results have established that aside from structural considerations, the boundary lipid, at least in the reconstituted cytochrome c oxidase, is a necessary but not sufficient condition for the enzymatic expression of cytochrome c oxidase.
Can J Biochem 1978 Sep
PMID:Spin-label study of the relation between enzymatic activity and lipid-protein organization in reconstituted cytochrome c oxidase. 21 92

A cytoplasmic "petitie" mutant of Saccharomyces cerevisiae (DS200/A1) has been isolated and determined to contain mitochondrial genetic markers in the oxi 1 locus. This locus has previously been reported to code for the structural gene of subunit 2 of cytochrome oxidase (Cabral et al. (1978) J. Biol. Chem. 243, 297-304). The segment of mitochondrial DNA retained in DS200/A1 has a repeat length of approximately 4500 base pairs and based on DNA sequencing contains a 756-nucleotide-long sequence that has been identified as the structural gene of subunit 2 of cytochrome oxidase. The presumptive gene sequence generates an amino acid sequence consistent with the reported molecular weight and composition of subunit 2 of yeast cytochrome oxidase. The correctness of the deduced amino acid sequence is further supported by its extensive homology to the primary structure of bovine cytochrome oxidase. The DNA segment of DS200/A1 has been located on the wild type mitochondrial DNA by comparative restriction mapping. The orientation of the COOH and NH2 termini and the direction of transcription of the gene have been determined.
J Biol Chem 1979 Sep 25
PMID:Assembly of the mitochondrial membrane system. DNA sequence of subunit 2 of yeast cytochrome oxidase. 22 27

A procedure for the ultrastructural cytochemical localization of cytochrome oxidase via cytochrome c in the cerebral cortex is described. Vascular perfusion fixation by formaldehyde and glutaraldehyde of different concentrations and mixtures of the two gave varying results. A mixture of 4% formaldehyde and 0.5% glutaraldehyde gave the best combination of ultrastructural preservation and retention of enzyme activity. Histochemical methods were examined for optimum incubation conditions, based on the oxidative polymerization of 3,3'-diaminobenzidine (DAB) to an osmiophilic product. The reaction product was discretely localized within intercristate and the intermembrane space of mitochondria. The staining pattern was the same in nerve cells and in neuroglia and their processed. The DAB reaction product was also found in mitochondria of the endothelial cells.
J Histochem Cytochem 1979 Sep
PMID:Ultrastructural demonstration of cytochrome oxidase via cytochrome C in cerebral cortex. 22 80

The effects of dietary copper level on tissue activities of the copper containing superoxide dismutase (CuSOD) were investigated, and these activities related to those of other copper containing enzymes particularly cytochrome oxidase. Male weaning rats were fed a basal diet (containing 0.8 mg Cu/kg) or this diet supplemented with 4 or 24 mg Cu/kg. After 6 weeks, rats fed the basal diet were then repleted using the high copper diet. In the two copper supplemented groups, no differences were observed in any of the parameters measured. In these groups, tissue activities of CuSOD were in the order of liver greater than kidney greater than RBC greater than testis greater than heart greater than brain greater than lung greater than muscle. In the basal group, CuSOD activity decreased in liver; RBC and heart to 14, 25, and 61%, respectively, of control activities after 6 weeks' depletion; tissues other than brain or muscle showed smaller but significant changes. Conversely, heart and muscle cytochrome oxidase activities decreased to 30 and 45% of control activity and liver to 70%. With repletion, CuSOD activities in liver and heart increased more rapidly than did cytochrome oxidase activities. It is concluded that liver CuSOD activity, which is normally high, is greatly reduced with little change in cytochrome oxidase activity; the reverse is found for heart and muscle tissue. The relevance of these changes to the maintenance of tissue integrity is discussed.
J Nutr 1979 Sep
PMID:Changes in activity of the Cu-Zn superoxide dismutase enzyme in tissues of the rat with changes in dietary copper. 22 57

1. The cytochrome-alpha alpha 3-deficient mi-3 cytoplasmic mutant of Neurospora crassa synthesizes a mitochondrial translation product which crossreacts with antibodies specific to subunit 1 of cytochrome oxidase. The immunoprecipitated polypeptide migrates more slowly during gel electrophoresis than the authentic 41 000-Mr subunit 1 of the wild-type enzyme. An apparent molecular weight of about 45 000 was estimated for the mutant product. 2. Radioactive labelling experiments in vivo show that the crossreacting material found in the mutant is relatively stable and does not form complexes with other subunits of the oxidase. 3. After induction of a functional cytochrome oxidase in the mutant cells with antimycin A, the 45 000-Mr polypeptide is converted to a 41 000-Mr component, which exhibits the same electrophoretic mobility as subunit 1 of the oxidase. Pulse-chase labelling kinetics reveal a typical precursor product relationship. 4. The converted polypeptide becomes assembled with other enzyme subunits to form a protein complex which has the immunological characteristics of cytochrome oxidase. A possible physiological role of the post-translational processing of the mitochondrially synthesized component is discussed.
Eur J Biochem 1979 Sep
PMID:Conversion of a mitochondrial precursor polypeptide into subunit 1 of cytochrome oxidase in the mi-3 mutant of Neurospora crassa. 22 83

Cytochrome a-type terminal oxidases derived from Thiobacillus novellus and Nitrobacter agilis have been purified to a homogeneous state as judged from their electrophoretic behavior and their subunit structures studied by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The T. novellus enzyme is composed of two kinds of subunits of 32,000 and 23,000 daltons and its minimum molecular weight is 55,000 on the basis of heme content and amino acid composition. The N. agilis enzyme also has two kinds of subunits of 40,000 and 27,000 daltons and its minimum molecular weight is 66,000 on the basis of heme content and amino acid composition. Therefore, the molecule of each enzyme is composed of two kinds of subunits which resemble the subunits of the eukaryotic cytochrome oxidase biosynthesized in the mitochondrion at least with respect to molecular weight.
J Biochem 1979 Sep
PMID:Subunits of cytochrome a-type terminal oxidases derived from Thiobacillus novellus and Nitrobacter agilis. 22 3

Human platelet plasma membranes were isolated with polylysine beads according to the technique developed by Jacobson and Branton (1977, Science [Wash. D. C.] 195:302--304). Lactoperoxidase-catalyzed surface iodination revealed that ninefold greater 125I specific activity was associated with the membranes isolated on beads than with whole platelets. Enrichment in the bead membrane preparation of the activities of membrane marker enzymes, bis(p-nitrophenyl)phosphate phosphodiesterase and Na,K-ATPase, was 8.0 and 4.4, respectively. Contamination with enzymes of other organelles, cytochrome oxidase and beta-glucuronidase, was relatively low as compared with membranes isolated by sucrose gradient centrifugation. Analysis by SDS polyacrylamide gel electrophoresis showed that a full complement of surface glycoproteins was present on the membranes isolated with polylysine beads. The polylysine bead technique is a rapid, reproducible and efficient method for the preparation of relatively pure platelet plasma membranes.
J Cell Biol 1979 Sep
PMID:Isolation of human platelet plasma membranes with polylysine beads. 22 8


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