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

---

Query: EC:1.9.3.1 (cytochrome oxidase)
8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of cyanide to both oxidized and ascorbate-reduced forms of Pseudomonas cytochrome c-551 oxidase was investigated. Spectral studies on the oxidized enzyme and its apoprotein showed that the ligand can bind to both the c and d, haem components of the molecule, and kinetic observations indicated that both chromophores reacted, under a variety of conditions, with very similar rates. Cyanide combination velocities were dependent on ligand concentration, and increasing the pH also accelerated the reaction; the second-order rate constant was estimated as approx. 0.2M-1 . s-1 at pH 7.0. The binding of cyanide to the protein was observed to have a considerable influence on reduction of the enzyme by ascorbate. Spectral and kinetic observations have revealed that the species haem d13+-cyanide and any unbound haem c may react relatively rapidly with the reductant, but the behaviour of cyanide-bound haem c indicates that it may not be reduced without prior dissociation of the ligand, which occurs relatively slowly. The reaction of reduced Pseudomonas cytochrome oxidase with cyanide is radically different from that of the oxidized protein. In this case the ligand only binds to the haem d1 component and reacts much more rapidly. Stopped-flow kinetic measurements showed the binding to be biphasic in form. Both the rates of these processes were dependent on cyanide concentration, with the fast phase having a second-order rate constant of 9.3 X 10(5) M-1 . s-1 and the slow phase one of 2.3 X 10(5) M-1 . s-1. The relative proportions of the two phases also showed a dependency on cyanide concentration, the slower phase increasing as the cyanide concentration decreased. Computer simulations indicate that a reaction scheme originally proposed for the reaction of the enzyme with CO is capable of providing a reasonable explanation of the experimental results. Static-titration data of the reduced enzyme with with cyanide indicated that the binding was non-stoicheiometric, the ligand-binding curve being sigmoidal in shape. A Hill plot of the results yielded a Hill coefficient of 2.6.
...
PMID:The reactions of Pseudomonas cytochrome c-551 oxidase with potassium cyanide. 3 76

Cytoplasmic membranes of Bacillus subtilis, grown in complex medium containing glucose, were fractionated into three membrane subfractions [light band (1.155 - 1.158 g/cm3); medium band (1.181 - 1.183 g/cm3); heavy band (1.21 - 1.25 g/cm3)] by sucrose density gradient centrifugation. Among these subfractions, the light and medium bands consisted mainly of membranes but the heavy band consisted of an irregular arrangement or aggregate of small globular protein components of 5 - 8 nm in diameter. We named this H-protein. H-protein formed trilamellar unit membrane structure when combined with lipid. In pulse-labeling and pulse-chase experiments with radioactive leucine, it was found that H-protein consisted of the newest membrane protein synthesized in the cells and the label incorporated into H-protein was shifted into light and medium band of the membranes during the chase. Cytochromes were not found in H-protein. However, when H-protein was incubated with haem alpha and protohaem, these compounds were incorporated into the apoproteins of the cytochromes present in H-protein and form cytochromes a and b. Cytochromes were also formed in H-protein which were isolated from the cells grown in the presence of haemin (haemin-grown H protein). Succinate dehydrogenase activity was increased about 4-fold by combining H-protein or haemin-grown H protein with lipid. H-protein had no cytochrome oxidase activity; however, haemin-grown H protein was found to have some of the activity and this was increased about 4-fold by combining the protein with lipid. Haemin-grown H protein was also found to form succinate: cytochrome c oxidoreductase when combined with lipid and vitamin K2. On the other hand, succinate oxidase was required for the addition of lipid, vitamin K2 and cytochrome c. NADH oxidase was also found in haemin-grown H protein and was activated about 9-fold in constituted reaction systems. Vesicles formed by haemin-grown H protein and lipid, could accumulate alanine and proline by addition of NADH or reduced phenazine methosulfate. Alanine and proline was also accumulated into the vesicles when transport energy was supplied as a membrane potential introduced by K+-diffusion via valinomycin. These results would indicate that H-protein contains the apoprotein of cytochromes, and a carrier involved in the active transport of alanine and proline.
...
PMID:Isolation and characterization of hydrophobic proteins (H proteins) in the membrane fraction of Bacillus subtilis. Involvement in membrane biosynthesis and the formation of biochemically active membrane vesicles by combining H proteins with lipid. 18 52

Aspects of the utilization of copper by the fungus, Dactylium dendroides, have been studied. The organism grows normally at copper levels below 10 nM. Cells grown in medium containing 30 nM copper or less concentrate exogenous metal at all levels of added copper; copper uptake is essentially complete within 15 min and is not inhibited by cycloheximide, dinitrophenol or cyanide. These results indicate that copper absorption is not an energy-dependent process. The relationship between fungal copper status and the activities of three copper-containing enzymes, galactose oxidase, and extracellular enzyme, the cytosolic, Cu/Zn superoxide dismutase and cytochrome oxidase, has also been established. The synthesis of galactose oxidase protein (holoenzyme plus apo-enzyme) is independent of copper concentration. Cells grown in copper-free medium (less than 10 nM copper) excrete normal amounts of galactose oxidase as an apoprotein. At medium copper levels below 5 micrometer, new cultures contain enough total copper to enable the limited number of cells to attain sufficient intracellular copper to support hologalactose oxidase production. As a result of cell division, however, the amount of copper available per cell drops to a threshold of approx. 10 ng/mg below which point only apogalactose oxidase is secreted. Above 5 micrometer medium copper, holoenzyme secretion is maintained throughout cell growth. The levels of the Cu/Zn superoxide dismutase respond differently in that the protein itself apparently is synthesized in only limited amounts in copper-depleted cells. Total cellular superoxide dismutase activity is maintained under such conditions by an increase in activity associated with the mitochondrial, CN(-)-insensitive, manganese form of this enzyme. Cells grown at 10 micrometer copper show 83% of their superoxide dismutase activity to be contributed by the Cu/Zn form compared to a 17% contribution to the total activity in cells grown at 30 nM copper, indicating that the biosynthesis of the Cu/Zn and Mn-containing enzymes is coordinated. The data show that the level of copper modulates the synthesis of the cytosolic superoxide dismutase. In contrast, the cytochrome oxidase activity of D. dendroides is independent of cellular copper levels obtainable. Thus, the data also suggest that these three enzymes utilize different cellular copper pools. As cells are depleted of copper by cell division, the available copper is used to maintain Cu/Zn superoxide dismutase and cytochrome oxidase activity; at very low levels of copper, only the latter activity is maintained. The induction of the manganisuperoxide dismutase in copper-depleted cells should have practical value in the isolation of this protein.
...
PMID:The utilization of copper and its role in the biosynthesis of copper-containing proteins in the fungus, Dactylium dendroides. 56 46

Mitochondrial cytochrome c is a water-soluble protein in the intermembrane space which catalyzes electron transfer from the cytochrome bc1 complex to the terminal oxidase cytochrome aa3. In Bradyrhizobium japonicum, a gene (cycM) which apparently encodes a membrane-anchored homolog of mitochondrial cytochrome c was discovered. The apoprotein deduced from the nucleotide sequence of the cycM gene consists of 184 amino acids with a calculated Mr of 19,098 and an isoelectric point of 8.35. At the N-terminal end (positions 9 to 31), there was a strongly hydrophobic domain which, by forming a transmembrane helix, could serve first as a transport signal and then as a membrane anchor. The rest of the protein was hydrophilic and, starting at position 72, shared about 50% sequence identity with mitochondrial cytochrome c. The heme-binding-site motif Cys-Gly-Ala-Cys-His was located at positions 84 to 88. A B. japonicum cycM insertion mutant (COX122) exhibited an oxidase-negative phenotype and apparently lacked cytochrome aa3 in addition to the CycM protein. The wild-type phenotype with respect to all characteristics tested was restored by providing the cycM gene in trans. The data supported the conclusion that the assembly of cytochrome aa3 depended on the prior incorporation of the CycM protein in the cytoplasmic membrane.
...
PMID:The Bradyrhizobium japonicum cycM gene encodes a membrane-anchored homolog of mitochondrial cytochrome c. 165 67

The wheat mitochondrial gene for apocytochrome b (CYB) has been identified by its hybridization to a yeast CYB probe and its nucleotide sequence has been determined. The wheat CYB sequence predicts a cytochrome b apoprotein of 398 amino acids; it is almost identical to that of maize but has ten additional amino acids at the carboxy terminus. No introns are present in the wheat CYB gene, but an internal segment of the gene is repeated at another genomic location. Transcript analysis reveals a single wheat CYB mRNA of approximately 2.4 kb with a long untranslated leader. Sequences upstream of the CYB coding region are very similar in wheat and maize but the stretch proposed to be a ribosome binding site in maize is not conserved in wheat. The corresponding leader regions of the wheat mitochondrial mRNAs for cytochrome oxidase subunits I and II also lack complementarity to the 3'-end of the small subunit rRNA. We conclude that alternative signals are involved in the initiation of translation in plant mitochondria.
...
PMID:The wheat mitochondrial gene for apocytochrome b: absence of a prokaryotic ribosome binding site. 298 49

Transition metal ions and superoxide participate in different autoxidations to a variable extent. In the reaction of 6-hydroxydopamine (6-OHDA) with oxygen at pH 7.0 or 8.0, addition of 5 to 300 U/ml superoxide dismutase inhibited autoxidation by up to 96% at the highest concentrations. Superoxide dismutase at concentrations of 5-20 U/ml inhibited by less than 40% when present alone, but inhibited by over 99% in the presence of desferrioxamine or histidine. EDTA also enhanced the inhibition by 20 U/ml superoxide dismutase to 86%, even though EDTA accelerated the autoxidation of 6-OHDA when present alone or with desferrioxamine. In contrast, other ligands, such as ADP or phytic acid, had little or no effect on inhibition by superoxide dismutase. Proteins such as albumin, cytochrome oxidase, or denatured superoxide dismutase also enhanced inhibition by active superoxide dismutase from less than 40% to over 90%. Evidently, in the presence of redox active metals, autoxidation occurs by inner sphere electron transfer, presumably within a ternary 6-OHDA.metal.oxygen complex. This mechanism does not involve free O2-. and is not inhibited by superoxide dismutase. On the other hand, the presence of certain ligands (including proteins) diminishes the ability of trace metals to exchange electrons with 6-OHDA or oxygen by an inner sphere mechanism. These ligands render autoxidation dependent on propagation by O2-. and therefore inhibitable by superoxide dismutase. Previously conflicting reports that superoxide dismutase alone inhibits 6-OHDA autoxidation are thus explicable on the basis that at sufficient concentration the apoprotein coordinates trace metals in such a way to preclude inner sphere metal catalysis.
...
PMID:Interactions between metals, ligands, and oxygen in the autoxidation of 6-hydroxydopamine: mechanisms by which metal chelation enhances inhibition by superoxide dismutase. 312 61

The significance of the exposed haem edge in cytochrome c was directly probed by chemically modifying the partially exposed haem propionate in the crevice region around residues threonine-78 and threonine-49. Reaction of tuna heart cytochrome c with a water-soluble carbodi-imide at pH 3.7 in the absence of any added nucleophilic base leads to the covalent addition of substituted N-acylureas to the protein at two sites. One site has been shown to be a haem propionate by isotope-tracer and i.r.-spectral analysis of haem purified from the apoprotein. The other site is aspartial acid-62 on the back of the molecule. The modified cytochrome c demonstrates abnormal properties, including auto-oxidizability, a reduction potential of + 105mV, a reversible transition to a high-spin species below pH 5.3, no 695 nm charge-transfer band in the ferric state and abnormal binding to mitochondrial membranes. The derivative does react with cytochrome oxidase in deoxycholate-treated submitochondrial particles or in purified preparations with a specific activity of 43-65% compared with that obtained with native cytochrome c. The results are consistent with the view that an intact haem crevice is essential for normal values for physiochemical characteristics, but the significant residual enzymic activity suggests that the electron-transfer interface and/or the cytochrome oxidase-binding site cannot be localized solely in the region of the exposed haem propionate.
...
PMID:Chemical modification of the haem propionate of cytochrome c. 624 79

1. Mitochondrial translation products of yeast Saccharomyces cerevisiae were separated according to charge as well as molecular weight by a highly resolving two dimensional electorphoretic technique (isoelectric focusing in the first dimension ana SDS-electrophoresis in the second dimension). 2. The major protein components (the oligomeric form of subunit 9 of mitochondrial ATPase, var 1, cytochrome oxidase subunits I, II and III, subunit 6 of mitochondrial ATPase and cytochrome b apoprotein) were identified either from their mobility in SDS-electrophoresis or by using mit- mutants defective in certain mitochondrially made polypeptides. 3. This method allowed the separation of subunit III of cytochrome oxidase and subunit 6 of mitochondrial ATPase which cannot be resolved by conventional SDS-polyacrylamide gel electrophoresis. 4. Subunit II of cytochrome oxiodase resolves in two spots of similar pI values and subunit 6 of mitochondrial ATPase resolves in two spots of similar molecular weight. In both cases the double spots disappear simultaneously following a single mutation in the coresponding structural gene. 5. Total mitochondrial proteins were also resolved two-dimensionally revealing over 100 components. The mitochondrial translation products, with the exception of subunit 9 of mitochondrial ATPase, could be easily recognized among the other mitochondrial proteins.
...
PMID:Biogenesis of mitochondria. Two-dimensional electrophoretic analysis of mitochondrial translation products in yeast. 625 Jun 20

Mitochondrial adenosine triphosphatase isolated from a double mutant of Saccharomyces cerevisiae lacking cytochrome b apoprotein and subunit II of cytochrome oxidase does not contain the mitochondrial translation product (approximate molecular weight, 32,000) previously suggested to be a subunit of the enzyme complex.
...
PMID:The largest mitochondrial translation product copurifying with the mitochondrial adenosine triphosphatase of Saccharomyces cerevisiae is not a subunit of the enzyme complex. 626 Jul 57

The biosynthesis of mammalian mitochondrial cytochromes was explored in primary hepatocyte cultures. When these were pulsed with [35S]methionine in the presence of cycloheximide, eight discrete mitochondrial polypeptides were detected by fluorography after their resolution under denaturing conditions by polyacrylamide gel electrophoresis. Since the pulse labeling of the polypeptides was sensitive to chloramphenicol, an inhibitor of mitochondrial translation, they must be translated on mitochondrial ribosomes. Three were identified as the largest subunits of cytochrome oxidase by their immunoprecipitation with antibody directed against purified rat liver cytochrome oxidase. Another (Mr = 28,000) was identified as one of eight subunits of purified rat liver cytochrome b-c1 complex by its immunoprecipitation with antibody directed against bovine heart b-c1 complex. Since cytochrome b apoprotein is the only product of the mitochondrial genome in the yeast cytochrome b-c1 complex (Krieke, J., Bechmann, H., van Hemert, F. J., Schweyan, R. J., Boer, P. H., Kaudewitz, F., and Groot, G. S. P. (1979) Eur. J. Bio-chem. 101, 607-617), the results strongly suggest that the Mr = 28,000 subunit of liver b-c1 complex is cytochrome b apoprotein. Thus the contribution of the mitochondrial translation system to the cytochrome complexes in liver is identical to that of yeast and Neurospora, and there appears to be no deletion or transfer to the nuclear genome of structural genes for mitochondrially synthesized cytochromes during eukaryotic evolution.
...
PMID:Site of synthesis of the mitochondrial cytochromes in hepatocyte cultures. 626 20


1 2 Next >>

---