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)

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.
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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

The purpose of this experimental investigation was to provide a purified plasma membrane fraction containing a highly hormone-responsive adenylate cyclase system. Bovine adrenal cortex was homogenised and a washed pellet (450 000 X g - min) was fractionated by zonal centrifugation in a sucrose and dextran gradient. Adenylate cyclase activity was purified up to 60-fold to a specific activity of 55, 340 and 210 pmol of adenosine 3':5'-monophosphate (cyclic AMP) produced/minute per mg of protein at 38 degrees C for the basal, adrenocorticotrophin and fluoride-activated states, respectively. The time course of the adenylate cyclase activity is linear. The concentration necessary for half-maximal stimulation by adrenocorticotrophin-(1-24)-tetracosipeptide is 0.5 muM. The high hormone-responsiveness of the membrane preparation allows one to demonstrate activation of adenylate cyclase by very weakly agonistic adrenocorticotrophin fragments. The F- activated state can be detergent-dispersed by Lubrol and shows a Km (ATP) different from that of either the basal or adrenocorticotrophin-stimulated state. Other marked enzymes such as 5'-nucleotidase, glucose-6-phosphatase and cytochrome oxidase were followed during purification. The plasma membrane fraction shows rather homogeneous, relatively large vesicles (mean diameter 0.5 mum). It contains high-affinity binding sites for angiotensin II (about 2 pmol per mg protein) with an apparent association constant of 2 X 10(7) (1/mol) at 12 degrees C. The yield, 20 mg of membrane protein per preparation, may make it a tool in either affinity-labelling studies with the peptide hormones mentioned or the starting point for solubilisation and purification of adenylate cyclase.
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PMID:Purification of bovine adrenal-cortex plasma-membrane vesicles containing a highly corticotropin-sensitive adenylate-cyclase system and angiotensin-II-binding sites. 19 4

Biological membranes are essentially asymmetric two-dimensional solutions of proteins in a bimolecular lipid layer. The overall structure and many physical properties of biological membranes can be explained by the fact that membrane proteins and membrane lipids contain hydrophilic as well as hydrophobic domains. Most biological properties of the membrane are determined by the membrane proteins which can catalyze directional processes. With the membrane protein cytochrome oxidase it will be demonstrated how the three-dimensional arrangement of membrane proteins can be studied by chemical, fluorometric, and electron optical methods. However, it is in most cases still impossible to explain the function of a membrane on the basis of its molecular architecture.
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PMID:[Structure and function of biological membranes (author's transl)]. 22 44

The isolation and chemical characterization of polypeptide IV from beef heart cytochrome oxidase is described. The protein is one of the main (stoichiometric) components of the oxidase. It is the largest polypeptide of the enzyme synthezised in the cytoplasm and has, as such, also been identified in enzyme preparations from yeast and Neurospora. A partial sequence, consisting of 105 amino acid residues which give a frame work of the covalent structure of the polypeptide is obtained from N- anc C-terminal sequencing and from the cyanogen bromide fragments of the chain. The isolation and sequencing of the fragments of this membrane protein are discussed.
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PMID:Studies on cytochrome c oxidase, V. Polypeptide IV: alignment and amino acid sequences on cyanogen bromide fragments. 22 79

The complete primary structure of the cytoplasmically synthesized polypeptide IV from beef heart cytochrome oxidase was determined via isolation and sequencing of overlapping methionine, tryptophan, and arginine fragments. The protein consists of 147 amino acids (Mr 17153). It is characterized as a part of a membrane protein complex by a hydrophobic segment consisting of 19 residues. It is suggested that this segment contacts the lipids of the inner mitochondiral membrane. Additional specific contacts may result from pairwise formation of salt bridges between ionic groups of the protein and the phospholipids. The function of this component of the terminal oxidase is yet unknown.
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PMID:Studies on cytochrome c oxidase, VI. Polypeptide IV. the complete primary structure. 22 80

1. Anti-heart mitochondria autoantibodies were developed in serum from dogs following experimental myocardial infarction. 2. Heart mitochondria frozen and thawed repeatedly in a sucrose/Tris-chloride buffer retained both their functional integrity as measured by the respiratory control ratio and their ability to serve as an antigen in a complement fixation test. Mitochondria frozen and thawed in a potassium chloride/Tris-chloride buffer lost both their functional integrity and their autoantigenic activity after one freeze-thaw cycle. 3. Extraction of the heart mitochondria with acetone/water mixtures to remove phospholipids from the membrane led to a complete loss of the ability of the mitochondria to react in the complement fixation test but did not affect the ability of the membranes to bind autoantibody in absorption experiments. 4. Treatment of the mitochondrial membranes with increasing concentrations of trypsin caused a loss of up to approximately 50% of the membrane protein with a gradual decrease in the autoantigenic activity of the membrane without impairment of the ability of the membrane to bind autoantibody. 5. Removal of up to 90% of the sialic acid of the mitochondrial membrane with neuraminidase resulted in a considerable increase in the complement-fixing autoantigenic activity of the membrane without changing the apparent ability of the membrane to bind autoantibody in absorption experiments. 6. Exposure of mitochondrial membranes to autoantibody and complement caused an inhibition of both an inner mitochondrial membrane enzyme, i.e. cytochrome oxidase (48%) and an outer mitochondrial membrane enzyme, i.e. NADH cytochrome c reductase (rotenone insensitive) (37%).
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PMID:Characterization of autoantigenic sites on isolated dog heart mitochondria. 118 45

Some imidazoline and guanidinium antihypertensive drugs display high affinity for a nonadrenergic membrane protein, the imidazoline-guanidinium receptive site (IGRS), which is insensitive to catecholamine and physically distinct from alpha 2-adrenoceptor. In the present report, we characterized IGRS in human and rabbit liver using [3H]idazoxan as radioligand. By performing subcellular fractionation, we showed a significant increase in [3H]idazoxan binding sites on membrane fractions enriched in cytochrome oxidase activity, a mitochondrial marker. A further enrichment in [3H]idazoxan binding (53-fold with respect to the homogenate) was found in a purified preparation of mitochondrial outer membranes. This localization of IGRS will facilitate the characterization of its functional activity in liver.
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PMID:Characterization of mitochondrial imidazoline-guanidinium receptive sites (IGRS) in liver. 131 14

Imidazoline-guanidinium-receptive site (IGRS) is a membrane protein that, even if recognized by a series of imidazoline and guanidinium alpha 2-adrenergic compounds, is insensitive to catecholamine and physically distinct from alpha 2 receptors (Parini, A., Coupry, I., Graham, R. M., Uzielli, I., Atlas, D., and Lanier, S. M. (1989) J. Biol. Chem. 264, 11874-11878). In the present report, we defined the subcellular localization of IGRS by performing binding studies with the imidazoline radioligand [3H]idazoxan. Binding studies on subcellular fractions of homogenates from human and rabbit liver showed a significant increase in [3H]idazoxan binding in a membrane fraction enriched in cytochrome oxidase activity, a specific marker for mitochondria. The enrichment in [3H]idazoxan binding sites correlates closely with cytochrome oxidase activity in the nuclear, mitochondrial, plasma membrane, microsomal, and soluble fractions (r = 0.966, p less than 0.002) but not with the specific markers for other cell compartments, suggesting a major localization of IGRS in mitochondria. Separation of inner and outer mitochondrial membranes by digitonin treatment showed that [3H]idazoxan binding correlates positively with monoamine oxidase (r = 0.960) and negatively with cytochrome oxidase (r = -0.950) activities. In addition, in highly purified preparations of outer mitochondrial membranes obtained by hypotonic shock, [3H]idazoxan binding activity was 12.5-fold enriched with respect to intact mitochondria. Taken together, these data show, for the first time, that IGRS in human and rabbit liver are mainly associated with the outer mitochondrial membranes. This demonstration of the major mitochondrial localization of IGRS will facilitate the characterization of its functional activity in liver.
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PMID:Subcellular distribution of imidazoline-guanidinium-receptive sites in human and rabbit liver. Major localization to the mitochondrial outer membrane. 184 63

We made use of a homologous cell-free mitochondrial protein import system derived from the yeast Saccharomyces cerevisiae to investigate the coupling of protein synthesis and import. Mitochondrial precursor proteins were synthesized in a yeast lysate either in the presence or absence of isolated yeast mitochondria. We were, therefore, able to analyze protein import into mitochondria either in a strictly posttranslational reaction (when isolated mitochondria were added only after protein synthesis has been arrested by the addition of cycloheximide) or in a reaction in which synthesis and import were permitted to occur simultaneously. We found that the import of a precursor protein consisting of the amino-terminal mitochondrial targeting sequence of cytochrome oxidase subunit IV fused to mouse dihydrofolate reductase is very inefficient in a strictly posttranslational reaction, whereas efficient import is observed if precursor synthesis and import are coupled. The same result was obtained when we analyzed the import of bulk endogenous yeast mitochondrial proteins in this system. Finally, we found that the insertion of the yeast outer membrane protein porin is also several times more efficient when synthesis and insertion are coupled.
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PMID:Coupling of protein synthesis and mitochondrial import in a homologous yeast in vitro system. 184 92

The effect of chronic alcohol consumption on steady-state kinetic characteristics of cytochrome oxidase in rat liver was studied using submitochondrial particles prepared from ethanol-fed and control rats. Preparations from both control and alcoholic rats had equivalent apparent Km values for cytochrome c of 13 microM in the presence of phenazine methosulfate or 19 microM with N,N,N',N'-tetramethylphenylene diamine as oxidation-reduction mediators at physiological ionic strength. Both preparations showed comparable stimulation (approx. 3-fold) of oxidase activity following detergent solubilization of the membrane and similar temperature dependence for oxidase activity. Under all conditions, preparations from alcohol-fed rats displayed 30 to 50% lower rats of cytochrome oxidase activity per unit membrane protein than those from control rats. The diminution in specific activity per mg protein was accompanied by a similar decline in heme aa3 content, as has been noted in previous studies. When expressed on a turnover number basis, the molecular activity of cytochrome oxidase (natoms O/min per nmol heme a) was equivalent in both alcoholic and control preparations. The results indicate that the intrinsic kinetic characteristics of cytochrome oxidase are not changed by alcohol consumption. The data suggest that the characteristic decline in heme aa3 content and cytochrome oxidase specific activity seen in ethanol-fed rats does not arise from alterations in the accessibility of the oxidase towards cytochrome c, or from changes in bulk phase lipid composition or physical properties. The results support the conclusion that ethanol consumption decreases the membrane content of functionally active oxidase molecules, but does not change the catalytic properties of these oxidase molecules.
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PMID:Effects of chronic alcohol consumption on the steady-state kinetics properties of cytochrome oxidase in rat liver. 215 17


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