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)

Cytochrome c has been chemically modified by methylene blue mediated photooxidation. It is established that the methionine residues of the protein have been specifically converted to methionine sulfoxide residues. No oxidation of any other amino acid residues or the cysteine thioether bridges of the molecule occurs during the photooxidation reaction. The absorbance spectrum of methionine sulfoxide ferricytochrome c at neutrality is similar to that of the unmodified protein except for an increase in the extinction coefficient of the Soret absorbance band and for the complete loss of the ligand sensitive 695 nm absorbance band in the spectrum of the derivative. The protein remains in the low spin configuration which implies the retention of two strong field ligands. Spin state sensitive spectral titrations and model studies of heme peptides indicate that the sixth ligand is definitely not provided by a lysine residue but may be methionine-80 sulfoxide coordinated via its sulfur atom. Circular dichroism spectra indicate that the heme crevice of methionine sulfoxide ferri- and ferrocytochrome c is weakened relative to native cytochrome c. The redox potential of methionine sulfoxide cytochrome c is 184 mV which is markedly diminished from the 260 mV redox potential of native cytochrome c. The modified protein is equivalent to native cytochrome c as a substrate for cytochrome oxidase and is not autoxidizable at neutral pH but is virtually inactive with succinate-cytochrome c reductase. These results indicate that the major role of the methionine-80 in cytochrome c is to preserve a closed hydrophobic heme crevice which is essential for the maintainance of the necessary redox potential.
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PMID:Methionine sulfoxide cytochrome c. 0 10

Cytochrome c oxidase (EC 1.9.3.1) has been solubilized by use of the nonionic detergents were determined for the oxidation of ferrocytochrome c in air. The results indicate that the plant cytochrome c oxidase resembles mammalian preparations in its sensitivity towards ionic strength and pH of the assay buffer.
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PMID:Optimum pH and ionic strength for the assay of cytochrome c oxidase from pea cotyledon mitochondria. 2 Oct 27

Cytochrome c has two stimulatory effects on respiration of mitochondria especially those from wounded potato tuber. In the first place a stimulation of succinate- and NADH-consuming, antimycin-A-sensitive respiration, which reaches a maximal value at low cytochrome c concentrations, has been found. In the second place, at higher concentrations of cytochrome c a stimulation of NADH-consuming respiration occurs, which is antimycin-A-resistant, but KCN-sensitive. This antimycin-A-resistant, NADH-consuming respiration is absent, when no cytochrome c is added to the reaction medium. It is insensitive to metal chelators, to which the antimycin-A-and KCN-resistant plant mitochondrial alternative oxidase is sensitive. By measurements of NADH-cytochrome c reductase activities a corresponding antimycin-A-resistant NADH-cytochrome c reductase has been found, which is insensitive to osmotic shock treatment. A localization of this antimycin-A-resistant electron transport with NADH as the electron donor in the outer mitochondrial membrane is likely. In the mitochondrial preparations cytochrome c might stimulate by acting as an electron-carrier between the outer membrane reductase and the inner membrane cytochrome oxidase. A big increase of the outer membrane mediated electron transport in the mitochondria has been observed after wounding of potato tuber tissue. The ability of the tissue to produce this electron transport pathway after wounding disappeared after prolonged storage of the tubers. A possible function of this electron transport pathway in fatty acid desaturation during the wound-reaction is suggested.
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PMID:Cytochrome c dependent, antimycin-A resistant respiration in mitochondria from potato tuber (Solanum tuberosum L.). Influence of wounding and storage time on outer membrane NADH-cytochrome-c-reductase. 17 74

Cytochrome c oxidase from the inner membrane of yeast mitochondria consists of seven nonidentical protein subunits, three being synthesized on mitochondrial ribosomes (molecular weights I: 43 K, II: 34 K, and III: 24 K) and four being made on cytoplasmic ribosomes (molecular weights IV: 14 K, V: 12 K, VI: 12 K, and VII: 4.5 K). In the present study all four cytoplasmically synthesized subunits of the enzyme were isolated on a large scale using ion exchange chromatography and gel filtration. Their amino acid composition as well as their amino- and carbosy-terminal amino acid residues have been determined. Sequence determinations of subunits IV and VI are already in an advanced state. The sequence of subunit VI is characterized by a large amino-terminal stretch dominated by charged amino acid residues followed by a cluster of hydrophobic amino acids. The binding site of yeast cytochrome oxidase for cytochrome c was studied by chemical crosslinking experiments. The formation of a disulfide bridge between the two proteins was observed by using cytochrome c from yeast modified with 5-thionitrobenzoate at the cysteinyl residue in position 107. Alternatively, a disulfide between yeast cytochrome c and the oxidase could be formed directly by oxidation with copper phenanthroline. Gel electrophoresis of the crosslinked complexes in sodium dodecyl sulfate revealed a new protein band with an apparent molecular weight of 38 K. This new band appears to be derived from cytochrome c and from subunit III of cytochrome oxidase.
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PMID:Structure of cytochrome c oxidase from baker's yeast - a progress report. Preparation of four subunits for amino acid sequence determination and attempts to localize the cytochrome c binding site. 19 98

Cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase; EC 1.9.3.1) can be resolved into an electron transfer complex (ETC) and an ionophore transfer complex (ITC). Coupling requires an interaction between the moving electron in the ETC and a moving, positively charged ionophore-cation adduct in the ITC. The duplex character of cytochrome oxidase facilitates this interaction. The ITC mediates cyclical cation transport. It can be replaced as the coupling partner by the combination of valinomycin and nigericin in the presence of K(+) when cytochrome oxidase is incorporated into liposomes containing acidic phospholipids or by the combination of lipid cytochrome c and bile acids in an ITC-resolved preparation of the ETC. Respiratory control can be induced by incorporating cytochrome oxidase into vesicles of unfractionated whole mitochondrial lipid. The activity of the ITC is suppressed by such incorporation and this suppression leads to the emergence of respiratory control. The ionophoroproteins of the ITC can be extracted into organic solvents; some 50% of the total protein of cytochrome oxidase is extractable. The release of free ionophore is achieved by tryptic digestion of the ionophoroprotein. Preliminary to this release the ionophoroprotein is degraded to an ionophoropeptide. Electrogenic ionophores, as well as uncoupler, are liberated by such proteolysis. The ITC contains a set of ionophoroproteins imbedded in a matrix of phospholipid.
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PMID:Coupling in cytochrome c oxidase. 19 94

Oxidative titrations were performed on the electrostatic complex formed between cytochrome c and cytochrome aa3 at low ionic strength. Midpoint potentials of the redox centers in the proteins in 1:1 and 2:1 complexes were compared with those in mixtures of the cytochromes at high ionic strength. Computer simulations of all titrations yielded midpoint potentials for the components of cytochrome aa3 which were consistent with literature values for isolated cytochrome aa3 or mixture of cytochromes c and aa3. However, the unequal heme extinction coefficients observed previously (Schroedl, N.A., and Hartzell, C.R. (1977), Biochemistry 16, 1327) during oxidative titrations of cytochrome aa3 became equal in magnitude under these experimental conditions. The binding of cytochrome c to cytochrome aa3 changed the midpoint potentials of cytochrome aa3 by 15-20 mV, while the midpoint potentials for cytochrome c were altered by 50-60 mV. Careful analysis of these titrations including computer simulation revealed that cytochrome c was able to bind to cytochrome aa3 only after cytochrome aL2+ had become oxidized. When bound to cytochrome aa3, the midpoint potential of cytochrome c was 210 7V. Titrations performed under a carbon monoxide atmosphere revealed cytochrome aa3 midpoint potentials unchanged from reported values. Cytochrome c again exhibited a midpoint potential of 210 mV after binding to cytochrome aa3.
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PMID:Oxidative titrations of reduced cytochrome aa3: influence of cytochrome c and carbon monoxide on the midpoint potential values. 19 44

Cytochrome c oxidase activity and cytochromes b, (c+c1) and a(+a3) concentrations were determined in liver mitochondria from rats fed the following diets: controls (group 1) fed ad libitum, energy-restricted (group 2) and protein-deficient (group 3). The animals were fed for two time intervals, 3--5 and 7--9 weeks. At 3--5 weeks, the cytochrome oxidase specific activity (nmol cytochrome c oxidized/mg protein/min) and cytochrome concentrations (nmol/mg protein) were not different in groups 2 and 3 as compared to group 1. At 7--9 weeks, the cytochrome oxidase specific activity and concentrations of cytochromes b, (c+c1) and a(+a3) were significantly reduced in group 2 rats as compared to well-fed controls. The Michaelis-Menten constant, Km apparent for ferrocytochrome c, was significantly higher in group 2 as compared to group 1. In group 3 rats, cytochrome oxidase specific activity and cytochrome b, a(+a3) concentrations were not different from group 1 at 7-9 weeks. However, cytochrome (c+c1) concentration was higher in group 3, resulting in an elevated ratio of cytochrome (c+c1) to cytochrome a(+a3) as compared to groups 1 and 2.
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PMID:Rat liver mitochondrial cytochrome c oxidase and cytochromes in experimental protein-energy malnutrition. 20 90

Cytochrome c derivatives labeled with a 3-nitrophenylazido group at lysine 13, at lysine 22, or at both residues have been prepared. The interaction of the cytochrome c derivatives with beef heart cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in the presence of ultrviolet light results in formation of a covalent complex between cytochrome c and the oxidase. Using the lysine 22 derivative, the polypeptide composition of the oxidase is not modified, nor is its catalytic activity, whereas with the lysine 13 derivative, the gel electrophoretic pattern is altered and the catalytic activity of the complex diminished. The data are consisten with a specfic covalent interaction of the lysine 13 derivative of cytochrome c with the polypeptide of molecular weight 23,700 (Subunit II) of cytochrome c oxidase.
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PMID:Interaction of cytochrome c with cytochrome c oxidase. Photoaffinity labeling of beef heart cytochrome c oxidase with arylazido-cytochrome c. 20 34

Cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1) has been resolved into a pair of complexes of unequal molecular weight. The larger complex (electron transfer complex) contains exclusively the oxidation-reduction proteins characteristic of cytochrome oxidase; the smaller complex (ion transfer complex) shows exclusively the capability for cation-dependent induction of the fluorescence of 8-anilino-1-naphthalenesulfonic acid--a capability demonstrable in preparations of cytochrome oxidase. The duplex nature of cytochrome oxidase has important implications for the mechanism of energy coupling.
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PMID:Resolution of cytochrome oxidase into two component complexes. 21

Deuterium and 31P nuclear magnetic resonance have been employed in an investigation of the effect of cytochrome c oxidase (EC 1.9.3.1) on the structure of lecithin bilayers. Cytochrome c oxidase was isolated from beef heart mitochondria in lipid-free form and reconstituted as a functional enzyme in bilayers composed of synthetic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Two separate reconstitution experiments were performed in which the lipid was selectively deuterated either at the C-5' or at the C-14' segment of the palmitic acyl chain. The phospholipid-to-protein ratio of both reconstituted complexes was 0.74 (mg/mg), corresponding to about 200 molecules lipid per molecule cytochrome c oxidase. The deuterium quadrupole splitting deltanuQ, and the phosphorus chemical shielding anisotropy, deltasigma, of the cytochrome c oxidase-phospholipid recombinants were measured as a function of temperature and compared to the results obtained for the pure lipid membrane without protein for the pure lipid membrane without protein. deltanuQ and deltasigma are highly sensitive to the structural organization of the lipid membrane and these measurements demonstrate that the incorporation of cytochrome c oxidase into phosphatidylcholine bilayers leads to a more disordered conformational state of the lipids. This result can be explained by a rapid exchange between lipids in direct contact with hydrophobic protein and those further away from it (exchange rate greater than 10(4) Hz). The irregular protein surface is sensed by all lipid molecules and induces a more disordered bilayer structure. In contrast to previous interpretations, our measurements do not suggest a special type of boundary lipid.
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PMID:Lipid-protein interaction in reconstituted cytochrome c oxidase/phospholipid membranes. 21 16


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