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)

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.
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PMID:Assembly of the mitochondrial membrane system. DNA sequence of subunit 2 of yeast cytochrome oxidase. 22 27

Copper(I) coordination to olefin bonds in pyridine compounds containing di- and triisoprenyl substituent groups had been investigated. Results from Raman and optical spectroscopic studies in aqueous ethanolic solutions indicate formation of pi complexes of 1:1 stoichiometry, with K congruent to 10(4) M-1. Despite there being several potential Cu(I) ligation sites on the alkyl side chain, only a single olefin bond is coordinated. The data are consistent with a model comprising extensive folding of the isoprenyl groups in the polar medium, with Cu(I) binding occurring at the exposed olefin group on the terminal unit. Ligand-bridged binuclear ions were formed by simultaneous coordination of an oxidant metal ion, (NH3)5RuIII, to the pyridine ring nitrogen atoms and Cu(I) to side-chain olefin bonds. Electron-transfer pathways were determined by kinetic analysis; both rate laws and comparative redox rates for complexes containing a variety of 4-alkylpyridine ligands indicate reaction predominantly by intermolecular processes. No evidence for intramolecular electron transfer, i.e., from Cu(I) through the bridging ligand to the bound Ru(III) center, could be found. This result is discussed both in terms of its implications toward the existence of very similar pathways proposed for electron transfer between heme and copper redox sites in cytochrome oxidase and within the wider context of apparent differences in the fundamental mechanisms of electron transfer in biological particles and transition metal ions.
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PMID:Evaluation of the role of polyisoprenyl functional groups in biological electron transfer. Transition metal models. 42 28

The kinetics of electron transfer between cytochrome-c oxidase and ruthenium hexamine has been characterized using the native enzyme or its cyanide complex either solubilized by detergent (soluble cytochrome oxidase) or reconstituted into artificial phospholipid vesicles (cytochrome oxidase-containing vesicles). Ru(NH3)2+6 (Ru(II] reduces oxidized cytochrome a, following (by-and-large) bimolecular kinetics; the second order rate constant using the cyanide complex of the enzyme is 1.5 x 10(6) M-1 s-1, for the enzyme in detergent, and slightly higher for COV. In the case of COV the kinetics are not affected by the addition of ionophores. Upon mixing fully reduced cytochrome oxidase with oxygen (in the presence of excess reductants), the oxidation leading to the pulsed enzyme is followed by a steady state phase and (eventually) by complete re-reduction. When the concentrations of dioxygen and oxidase are sufficiently low (micromolar range), the time course of oxidation can be resolved by stopped flow at room temperature, yielding an apparent bimolecular rate constant of 5 x 10(7) M-1 s-1. After exhaustion of oxygen and end of steady state, re-reduction of the pulsed enzyme by the excess Ru(II) is observed; the concentration dependence shows that the rate of re-reduction is limited at 3 s-1 in detergent; this limiting value is assigned to the intramolecular electron transfer process from cytochrome a-Cua to the binuclear center. Using the reconstituted enzyme, the internal electron transfer step is sensitive to ionophores, increasing from 2-3 to 7-8 s-1 upon addition of valinomycin and carbonyl cyanide m-chlorophenylhydrazone. This finding indicates for the first time an effect of the electrochemical potential across the membrane on the internal electron transfer rate; the results are compared with expectations based on the hypothesis formulated by Brunori et al. (Brunori, M., Sarti, P., Colosimo, A., Antonini, G., Malatesta, F., Jones, M.G., and Wilson, M.T. (1985) EMBO J. 4, 2365-2368), and their bioenergetic relevance is discussed with reference to the proton pumping activity of the enzyme.
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PMID:Control of electron transfer by the electrochemical potential gradient in cytochrome-c oxidase reconstituted into phospholipid vesicles. 215 21

Cytochrome c oxidase can generate membrane potential in the absence of cytochrome c (e.g., in cytochrome c-deficient mitochondria or in proteoliposomes) with hexaammineruthenium as an artificial electron donor. Of several other redox mediators tested, phenazine methosulfate was found to be an efficient artificial substrate for membrane energization by cytochrome oxidase, whereas TMPD, DAD, DCPIP or ferrocyanide are virtually ineffective. The ability of Ru(NH3)6(2+) and phenazine methosulfate to support the generation of delta psi by cytochrome c-oxidase correlates with their effectiveness as electron donors to cytochrome a in the cyanide-inhibited membrane-bound enzyme.
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PMID:Hexaammineruthenium as an electron donor to mitochondrial cytochrome oxidase: membrane potential generation in the absence of cytochrome c. 300 96

When O2 was injected into an anaerobic suspension of valinomycin-treated rat liver mitochondria inhibited with rotenone, antimycin, and myxothiazol, a small amount of O2 (0.23-0.33 ng-atom of O/mg of protein) was reduced extremely rapidly (within the 2 s time-resolution of the oxygen electrode). The subsequent steady-state rate of flow of electrons to oxygen was very low [less than 3 nequiv. X s-1 X (g of mitochondrial protein)-1]. In the presence of valinomycin there was a rapid ejection of protons synchronous with the rapid phase of O2 consumption corresponding to 0.38-0.61 nequiv. of H+ X (mg of mitochondrial protein)-1. When valinomycin was replaced by carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) there was a rapid alkalification of the medium corresponding to 0.20-0.42 nequiv. of H+ X (mg of mitochondrial protein)-1. When 2 mM-Fe(CN)6(4-) was present to re-reduce endogenous cytochrome c, O2 consumption was still biphasic but the second phase of O2 consumption was very much more rapid [600 nequiv. X s-1 X (g of protein)-1], and resulted in the virtually complete consumption of the O2 in the pulse within 4 s. With 60 microM-Ru(NH3)6(2+) as reductant, O2 consumption was even faster [1200 nequiv. X s-1 X (g of protein)-1]. In a medium containing 150 mM-choline chloride with Ru(NH3)6(2+) as reductant, the proton per reducing equivalent stoichiometry (delta H+O/e-) was +0.95 in the presence of valinomycin and -0.94 in the presence of FCCP. In choline chloride medium containing Ru(NH3)6(2+) and valinomycin, there was an uptake of K+ ions corresponding to 1.86 K+/e-. It is concluded that nearly 1 proton is translocated outwards through cytochrome oxidase per oxidizing equivalent injected in this medium. In low ionic strength sucrose-based medium, with Ru(NH3)6(2+) as reductant, delta H+O/e- was 1.05 in the presence of valinomycin, and -0.71 in the presence of FCCP. It is concluded that the translocation of protons is accompanied by net acid production in this medium.
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PMID:Proton translocation by cytochrome oxidase in (antimycin + myxothiazol)-treated rat liver mitochondria using ferrocyanide or hexammineruthenium as electron donor. 302 18

We have isolated a cDNA clone for the precursor to subunit IV of bovine cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1). A cDNA library was constructed from poly(A)+ RNA of adult beef liver by insertion of cDNA into the plasmid vector pBR322. Transformants were screened by colony hybridization with two mixtures of [32P]-labeled synthetic oligodeoxyribonucleotides. We screened 20,000 transformants with a mixture of heptadecamers complementary to all 16 possible sequences encoding amino acids 98-103 and obtained two cDNA clones encoding subunit IV amino acid sequences. We determined the DNA sequence of the larger (416 base-pair) insert, which contains the coding sequence for amino acids 1-107 of the mature protein and an NH2-terminal extension (presequence). The deduced amino acid sequence of the mature protein is identical with the previously determined protein sequence: the sequence of the NH2-terminal extension contains a potential initiator methionine at amino acid -22 from the NH2-terminus of the processed protein. The presequence is quite basic and contains several arginines, including one at the processing site. No hydrophobic region analogous to that found in bacterial and eukaryotic signal peptides is present, but there are homologies with other mitochondrial protein presequences, which may include a common signal for their destination and processing.
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PMID:Isolation and characterization of a cDNA clone for bovine cytochrome c oxidase subunit IV. 609 95

When the calcium-transport inhibitor, ruthenium red, is chromatographed on a cation exchange resin, it yields a number of colored fractions and a colorless component that absorbs in the ultraviolet. The electron transfer activity previously ascribed to ruthenium red (Schwerzmann, K., Gazzotti, P., and Carafoli, E. (1976) Biochem. Biophys. Res. Commun. 69, 812) fractionates exclusively with the UV-absorbing material. On the basis of spectral, physical, and activity studies, we have identified this compound as Ru(NH3)62+/3+. It is shown that Ru(NH3)62+/3+ is an efficient electron donor directly to cytochrome oxidase, without mediation by cytochrome c. The steady state kinetics of electron transfer from Ru(NH3)62+ to purified oxidase resembles that of cytochrome c, showing a biphasic pattern but higher apparent Km values (Km1 = 8 microM, Km2 = 88 microM). Under conditions that favor tight binding to the oxidase, cytochrome c acts as a competitive inhibitor of Ru(NH3)62+, indicating that the two electron donors interact with cytochrome oxidase at the same site(s). The efficiency of Ru(NH3)62+ as an electron mediator to cytochrome aa3 and the similarity of its kinetic behavior to that of cytochrome c, make it a potentially valuable tool for investigating the mechanism of energy conservation in the terminal segment of the mitochondrial respiratory chain.
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PMID:An effective electron donor to cytochrome oxidase. Purification, identification, and kinetic characterization of a contaminant of ruthenium red, hexaamineruthenium II/III. 616 83

The amino acid sequence of subunit VI derived from bovine heart cytochrome oxidase has been completed and is a single polypeptide chain consisting of 85 amino acid residues. The sequence is: acetyl (formula: see text). The NH2 terminus of subunit VI is blocked with an acetyl group and the molecular weight of the native protein including the acetyl group is 10,067. From the sequence of subunit VI, it is obvious that this subunit corresponds to polypeptide VII of Steffens et al. (Steffens, G. C. M., Steffens, G. J., and Buse, G. (1979) Hoppe-Seyler's Z. Physiol. Chem. 360, 1641-1650).
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PMID:The complete amino acid sequence of bovine heart cytochrome oxidase subunit VI. 626 5

In yeast, the mitochondrial genes for subunit I of cytochrome oxidase (oxi3) and for apocytochrome b (cob) are known to be split. In some strains, the latter contains five intervening sequences, three of which coincide with clusters of mutational sites referred to in their order of transcription as the loci box3, 10, and 7, respectively. Mutations at the first of these result in the accumulation of novel, large polypeptides (apparent Mr congruent to 43,000) believed to originate from a fusion of sequences found in the NH2-terminal segment of apocytochrome b to others encoded in the intervening sequence itself. We now provide evidence for close similarities of at least a part of translated intron sequences between (a) mutants in box7 in "long" form and "short" form strains (which lack the first three introns including the one for the box3 locus); (b) mutants in a subset of box7 mutants and those in box3, and (c) between intron sequences in box7 and a sequence presumably encoded in oxi3. These structural homologies have been analyzed and shown to be referable to sequence homologies in two proteins, one derived from the second intron (box3) in cob and the other from oxi3. The accumulation in certain cob mutants of proteins and of a transcript containing a sequence specified by oxi3 provides additional strong evidence for the previously suggested regulation of oxi3 by the penultimate, box7-containing intron of cob.
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PMID:Evidence for translated intervening sequences in the mitochondrial genome of Saccharomyces cerevisiae. 627 26

The complete primary structure of bovine heart cytochrome c1 was established by analyses of peptide fragments prepared by digestion using trypsin, staphylococcal protease, and chymotrypsin and by cyanogen bromide cleavage of cytochrome c1 and its derivatives. The total number of amino acid residues is 241, giving a molecular weight of 27,924 including the heme group. The NH2- and COOH-terminal residues are serine and lysine, respectively. One characteristic of the protein is that cytochrome c1 contains 43.6% hydrophobic residues and the polarity is estimated to be 41.1%. No clear homology was found between cytochrome c1 and other membranous proteins such as cytochrome b5 or the subunits of cytochrome oxidase for which sequences have been reported. Cytochrome c1 is predicted to have a high content of alpha-helix (46%). Partial sequence studies were also carried out on cytochrome c1 preparations obtained by different procedures and showed that there is no difference among the sequences of various preparations of cytochrome c1. The presence of a hydrophobic cluster near the COOH-terminal region indicates that the COOH-terminal region of cytochrome C1 associates with, or is buried in, the phospholipid bilayer of the mitochondrial membrane.
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PMID:Structural studies of bovine heart cytochrome c1. 628 15


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