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)

Reconstituted cytochrome oxidase liposomes were fused with liposomes reconstituted with mitochondrial hydrophobic protein, which acts as a membrane-bound uncoupler of cytochrome oxidase. Fusion was assayed by the loss of respiratory control of cytochrome oxidase as measured by the increased rate of ascorbate oxidation induced by hydrophobic protein when both proteins shared the same vesicles. Fusion was dependent on the presence of phosphatidylserine in the liposomes Ca++ in the aqueous medium. Phosphatidylcholine-phosphatidylserine liposomes required higher concentrations of phosphatidylserine and Ca++ than did phosphatidylethanolamine-phosphatidylserine liposomes. Cytochrome oxidase vesicles containing high concentrations of phosphatidylserine showed little or no respiratory control, while those with lower concentrations showed high respiratory control; respiratory control could be induced by fusing cytochrome oxidase vesicles containing high phosphatidylserine with protein-free liposomes containing low phosphatidylserine concentration. If cytochrome oxidase vesicles and hydrophobic protein vesicles were prefused separately for 15 min, they lost the ability to fuse upon being subsequently mixed together. The reconstituted vesicles had diameters of about 200 A; fusion yielded vesicles with diameters in excess of 1000 A.
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PMID:Fusion of phospholipid vesicles reconstituted with cytochrome c oxidase and mitochondrial hydrophobic protein. 18 Feb 95

The acidic phospholipid cardiolipin was shown to be very efficient in promoting calcium-induced fusion of proteoliposomes. The degree of fusion was dependent on the phosphatidylethanolamine content of the vesicles. Addition of CaCl2 to proteoliposomes containing phosphatidylcholine and cardiolipin but without phosphatidylethanolamine did not induce fusion. Fusion of cytochrome oxidase vesicles, containing less than 50 mol% phosphatidylethanolamine resulted in monolamellar vesicles with a diameter of about 200 nm. The vesicles could be induced to fuse further by establishing an osmotic pressure across their membranes. When proteoliposomes containing more than 50 mol% phosphatidylethanolamine were fused, large vesicles with a diameter exceeding 1 micrometer were formed. They appeared in the electron microscope as a mixture of multilamellar and monolamellar vesicles. Fusion of corresponding liposomes resulted in formation of even larger structures appearing as dense multilamellar bodies and paracrystalline honeycomb-like lattices.
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PMID:Calcium-induced fusion of proteoliposomes and protein-free liposomes. Effect of their phosphatidylethanolamine content on the structure of fused vesicles. 23 55

In this study, we have investigated the protein/lipid interactions of two mitochondrial precursor proteins, apocytochrome c and pCOX IV-DHFR, which exhibit mitochondrial import pathways with different characteristics. In-vitro-synthesized apocytochrome c was found to bind efficiently and specifically to liposomes composed of negatively charged phospholipids and showed a (at least partial) translocation across a lipid bilayer, as reported previously for the chemically prepared precursor protein [Rietveld, A. & de Kruijff, B. (1984) J. Biol. Chem. 259, 6704-6707; Dumont, M. E. & Richards, F. M. (1984) J. Biol. Chem. 259, 4147-4156]. Negatively charged liposomes were shown to efficiently compete with mitochondria for import of in-vitro-synthesized apocytochrome c into the organelle, suggesting an important role for negatively charged phospholipids in the initial binding of apocytochrome c to mitochondria. In contrast, the purified and in-vitro-synthesized precursor fusion protein pCOX IV-DHFR, consisting of the presequence of yeast cytochrome oxidase subunit IV fused to mouse dihydrofolate reductase was unable to translocate across a pure lipid bilayer. The data indicate that the ability of apocytochrome c to spontaneously translocate across the bilayer is not shared by all mitochondrial precursor proteins. The implications of the special protein/lipid interaction of apocytochrome c for import into mitochondria will be discussed.
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PMID:Bilayer-penetrating properties enable apocytochrome c to follow a special import pathway into mitochondria. 131 82

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

A fusion protein was expressed in transgenic tobacco and yeast cells to examine the functional conservation of mechanisms for importing precursor proteins from the cytosol into mitochondria and chloroplasts. The test protein consisted of the mitochondrial leader peptide from the yeast precursor to cytochrome oxidase subunit Va (prC5) fused to the reporter protein chloramphenicol acetyltransferase. This protein, denoted prC5/CAT, was transported into the mitochondrial interior in yeast and tobacco cells. In both organisms, the mitochondrial form of prC5/CAT was smaller than the primary translation product, suggesting that proteolytic processing occurred during the transport process. prC5/CAT also was translocated into chloroplasts in vivo, accumulating to approximately the same levels as in plant mitochondria. However, accumulation of prC5/CAT in chloroplasts relative to mitochondria varied with the conditions under which plants were grown. The chloroplast form of prC5/CAT also appeared to have been proteolytically processed, yielding a mature protein of the same apparent size as that seen in mitochondria of either tobacco or yeast. Chloramphenicol acetyltransferase lacking a mitochondrial targeting peptide did not associate with either chloroplasts or mitochondria. The results demonstrated that in plant cells a single leader peptide can interact functionally with the protein translocation systems of both chloroplasts and mitochondria, and raised the possibility that certain native proteins might be shared between these two organelles.
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PMID:A yeast mitochondrial leader peptide functions in vivo as a dual targeting signal for both chloroplasts and mitochondria. 196 76

We report the first lateral diffusion measurements of redox components in normal-sized, matrix-containing, intact mitoplasts (inner membrane-matrix particles). The diffusion measurements were obtained by submicron beam fluorescence recovery after photobleaching measurements of individual, intact, rat liver mitoplasts bathed in different osmolarity media to control the matrix density and the extent of inner membrane folding. The data reveal that neither the extent of mitochondrial matrix density nor the complexity of the inner membrane folding have a significant effect on the mobility of inner membrane redox components. Diffusion coefficients for Complex I (NADH:ubiquinone oxidoreductase), Complex III (ubiquinol: cytochrome c oxidoreductase), Complex IV (cytochrome oxidase), ubiquinone, and phospholipid were found to be effectively invariant with the matrix density and/or membrane folding and essentially the same as values we reported previously for spherical, fused, ultralarge, matrix-free, inner membranes. Diffusion of proton-transporting Complex V (ATP synthase) appeared to be 2-3-fold slower at the greatest matrix density and degree of membrane folding. Consistent with a diffusion-coupled mechanism of electron transport, comparison of electron transport frequencies (productive collisions) with the theoretical, diffusion-controlled, collision frequencies (maximum collisions possible) revealed that there were consistently more calculated than productive collisions for all redox partners. Theoretical analyses of parameters for submicron fluorescence recovery after photobleaching measurements in intact mitoplasts support the finding of highly mobile redox components diffusing at the same rates as determined in conventional fluorescence recovery after photobleaching measurements in fused, ultralarge inner membranes. These findings support the Random Collision Model of Mitochondrial Electron Transport at the level of the intact mitoplast and suggest a similar conclusion for the intact mitochondrion.
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PMID:Lateral diffusion of redox components in the mitochondrial inner membrane is unaffected by inner membrane folding and matrix density. 200 33

Cytochrome-c oxidase from Bacillus stearothermophilus has been purified to homogeneity by detergent extraction followed by DEAE-cellulose, hydroxyapatite- and gel-filtration chromatography. The enzyme is a typical cytochrome-aa3-type oxidase which binds carbon monoxide and is sensitive to classical oxidase inhibitors like cyanide and azide. The purified enzyme is composed of three different subunits (57, 37 and 22 kDa). The subunit with intermediate molecular mass contains a covalently attached heme-c moiety. The enzyme appeared to be extremely thermostable (inactivation temperature = 81 degrees C). Highest turnover rates of the reconstituted enzyme were obtained with Saccharomyces cerevisiae cytochrome c or reduced forms of non-physiological electron donors like N,N,N',N'-tetramethyl-p-phenylenediamine and phenazine methosulphate. The reconstituted enzyme can generate a proton-motive force consisting of a high membrane potential and trans-membrane pH gradient. The high electro-motive force of the enzyme (delta p = -180 to -200 mV) indicates that this enzyme functions as a high-capacity electrogenic proton pump. Liposomes containing the purified thermostable and thermoactive cytochrome-c oxidase were fused with membranes from the fermentative bacterium Clostridium acetobutylicum. In the hybrid system a high proton-motive force can be generated upon oxidation of reduced N,N,N',N'-tetramethyl-p-phenylenediamine by the incorporated oxidase which subsequently can be used to drive secondary transport of amino acids. This demonstrates the applicability of the cytochrome-c oxidase to study solute transport in membranes of fermentative bacteria.
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PMID:Characterization and application of a thermostable primary transport system: cytochrome-C oxidase from Bacillus stearothermophilus. 253 27

An artificial mitochondrial precursor protein (the presequence of cytochrome oxidase subunit IV fused to mouse dihydrofolate reductase) binds to isolated yeast mitochondrial outer membranes and to liposomes whose phospholipid composition resembles that of outer membranes. In both cases, binding is strongly inhibited by low temperature or methotrexate (which stabilizes the dihydrofolate reductase moiety) and partly inhibited by adriamycin (which binds to acidic phospholipids). Binding is accompanied by partial unfolding of the protein. Binding of the urea-denatured fusion protein to outer membranes or liposomes is insensitive to low temperature, methotrexate, or adriamycin. These results, and those reported in the accompanying paper (Eilers, M., Endo, T., and Schatz, G. (1989) J. Biol. Chem. 264, 2945-2950) suggest that import of this fusion protein into isolated mitochondria involves at least partial unfolding by acidic phospholipids on the mitochondrial surface.
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PMID:Binding of a tightly folded artificial mitochondrial precursor protein to the mitochondrial outer membrane involves a lipid-mediated conformational change. 253 27

The terminal cytochrome c1aa3 of the respiratory chain of Thermus thermophilus has been isolated and purified to homogeneity by a novel procedure. The two subunit proteins (55 and 33 kDa) have been characterized chemically. Computer searches with partial amino acid sequences obtained from both subunits show that the larger subunit belongs to the cytochrome oxidase subunit I protein family while the smaller covalently heme-binding subunit is not a cytochrome c1 but appears to be a fused protein between cytochrome c and cytochrome oxidase subunit II. With respect to the 16-S rRNA-derived phylogeny of procaryotes, the results show that the genetic information for an O2-reacting cytochrome oxidase (EC 1.9.3.1) existed already in early eubacteria.
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PMID:Evidence for cytochrome oxidase subunit I and a cytochrome c--subunit II fused protein in the cytochrome 'c1aa3' of Thermus thermophilus. How old is cytochrome oxidase? 254 Sep 68

Both beef heart cytochrome oxidase and bacteriorhodopsin of Halobacterium halobium were reconstituted into liposomes by the sonication-cholate dialysis method. The proteoliposomes showed the respiratory control ratio of 4.2, and steady-state illumination of the vesicles lead to the 2.7-fold stimulation of the oxidase activity in the absence of uncouplers. The light-stimulated state 4 respiration increased with light intensity, but light had no effect on the oxidase activity that had been relieved by addition of uncouplers. Proteoliposomes with the photosensitive oxidase activity were also obtained when cytochrome oxidase vesicles were fused with bacteriorhodopsin vesicles in the presence of calcium chloride, and the extent of photoactivation was maximally 1.4-fold. The light-induced respiratory release was observed even in the presence of valinomycin or nigericin, indicating that the oxidase activity was sensitive to both the membrane potential and the pH gradient. We propose as a mechanism of the respiratory control that the process of proton transport to the reaction center for water formation is the rate limiting step for the cytochrome oxidase activity.
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PMID:A mechanism of respiratory control: studies with proteoliposomes containing cytochrome oxidase and bacteriorhodopsin. 282 80


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