Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:O95477 (membrane-bound)
 29,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A membrane-bound D-gluconate dehydrogenase [EC 1.1.99.3] was solubilized from membranes of Pseudomonas aeruginosa and purified to a homogeneous state with the aid of detergents. The solubilized enzyme was a monomer in the presence of at least 0.1% Triton X-100, having a molecular weight of 138,000 on polyacrylamide gel electrophoresis or 124,000--131,000 on sucrose density gradient centrifugation. In the absence of Triton X-100, the enzyme became dimeric, having a molecular weight of 240,000--260,000 on sucrose density gradient centrifugation. Removal of Triton X-100 caused a decrease in enzyme activity. Enzyme activity was stimulated by addition of phospholipid, particularly cardiolipin, in the presence of Triton X-100. The enzyme had a cytochrome c1, c-554(551), which might be a diheme cytochrome, and it also contained a covalently bound flavin but not ubiquinone. In the presence of sodium dodecyl sulfate, the enzyme was dissociated into three components with molecular weights of 66,000, 50,000, and 22,000. The components of 66,000 and 50,000 daltons corresponded to a flavoprotein and cytochrome c1, respectively, but that of 22,000 dalton remained unclear as to its function.
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PMID:Membrane-bound D-gluconate dehydrogenase from Pseudomonas aeruginosa. Purification and structure of cytochrome-binding form. 10 26

1. The uptakes of Pi and serine by whole cells of mutant strains of Escherichia coli K12, grown under both aerobic and anaerobic conditions, were studied. 2. Uptake by aerobic cells was low in a ubiquinone-less mutant but normal in two mutant strains unable to couple phosphorylation to electron transport. 3. One of these uncoupled strains, carrying the unc-405 allele, does not form a membrane-bound Mg2+-stimulated adenosine triphosphatase aggregate, and it is concluded that the Mg2+-stimulated adenosine triphosphatase does not serve a structural role in the aerobic active transport of Pi or serine. 4. The other uncoupled strain, in which aerobic uptake is unaffected, carries a mutation in the uncB gene, thus distinguishing this gene from the etc gene, previously shown to be concerned with the coupling of electron transport to active transport. 5. The uptakes of Pi and serine by anaerobic cells were normal in the ubiquinone-less mutant, but defective in both the uncoupled strains. 6. The uptake of Pi and serine by anaerobic cells of the uncB mutant could be increased by the addition of fumarate to the uptake medium. The unc-405 mutant, however, required the addition of fumarate for growth and for uptake. 7. The uncB mutant, unlike the unc-405 mutant, is able to grow anaerobically in a minimal medium with glucose as sole source of carbon. Similarly a strain carrying a mutation in the frd gene, which is the structural gene for the enzyme fumarate reductase, is able to grow anaerobically in a glucose-minimal medium. However, a mutant strain carrying mutations in both the uncB and frd genes resembles the unc-405 mutant in not being able to grow under these conditions.
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PMID:Metabolite transport in mutants of Escherichia coli K12 defective in electron transport and coupled phosphorylation. 12 86

Several mutants of Escherichia coli affecting aerobic energy generation and energization of the bacterial membrane have been examined for their effect on streptomycin and gentamicin accumulation and susceptibility. A heme-deficient mutant (K207) and two mutants (CJ-8 [colicin K insensitive] and NR-70) associated with defective aerobic active transport were associated with decreased transport of streptomycin and gentamicin and increased resistance to those antibiotics. These mutants also exhibited increased resistance to several other aminoglycoside antibiotics, but not the aminocyclitol spectinomycin. The same observations were made with a ubiquinone-deficient mutant, but a strA derivative of this mutant was shown additionally to be saturable for streptomycin accumulation at a concentration four or more times lower than that required for saturation of the parent. A mutant uncoupled for adenosine 5'-triphosphate synthesis from electron transport and membrane Mg-adenosine 5'-triphosphatase deficient was hypersensitive to those aminoglycosides tested and spectinomycin, and showed enhanced transport of streptomycin and gentamicin. A variety of compounds structurally related to streptomycin were examined at high concentrations for inhibition of streptomycin uptake in a strA mutant of E. coli K-12 SA 1306, but no evidence for competition was detected, suggesting the absence of a common transport carrier. Four different divalent cations were shown to inhibit streptomycin and gentamicin accumulation in E. coli K-12 SA 1306. Divalent cations were shown to inhibit uptake of these two drugs in two bacterial species with distinct cell wall structures, Pseudomonas aeruginosa and Staphylococcus aureus, and to inhibit streptomycin uptake in spheroplasts of streptomycin-susceptible and -resistant E. coli. However, calcium had almost no inhibitory effect on streptomycin uptake by the ubiquinone-deficient mutant E. coli AN66. These and previous findings have been used to formulate a model for aminoglycoside entry into bacteria using a low-affinity membranous complex involved in membrane energization that includes respiratory quinones, which probably act to bind and transport aminoglycosides across the cell membrane. This phase of transport is associated with the lowest accumulation rate (termed energy-dependent phase I) that is rate limiting for susceptibility. It is further proposed that subsequent association of the membrane-bound aminoglycoside with higher-affinity binding sites on membrane-associated ribosomes carrying out a normal ribosomal cycle and protein synthesis results in a more rapid transport rate (termed energy-dependent phase II). The increased rate could result from a state of membrane energization analogous to that causing enhanced aminoglycoside transport rates seen in the uncoupled mutant, AN120. How this model explains the mechanism by which enzymatically modified aminoglycosides render cells resistant to unmodified aminoglycosides is also discussed.
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PMID:Effects of membrane-energy mutations and cations on streptomycin and gentamicin accumulation by bacteria: a model for entry of streptomycin and gentamicin in susceptible and resistant bacteria. 14 38

The enzymatic activities and the cytochrome components of the respiratory chain were investigated with membrane fractions from chemoheterotrophically growth Rhodopseudomonas palustris. Whereas the level of electron transfer carriers was not distinctly affected by a change of the culture conditions, the potential activities of the enzymes were clearly increased when the cells were grown aerobically. Reduced-minus oxidized difference spectra of the membrane fractions prepared from dark aerobically grown cells revealed the presence of three beta-types cytochromes b561, b560 and b558, and at least two c-type cytochromes c556 and c2 as electron carriers in the electron transfer chain. Cytochrome of a-type could not be detected in these membranes. Reduced plus CO minus reduced difference spectra of the membrane fractions were indicative of cytochrome o, which may be equivalent to cytochrome b560, appearing in substrate-reduced minus oxidized difference spectra. Cytochrome o was found to be the functional terminal oxidase. CO difference spectra of the high speed supernatant fraction indicated the presence of cytochrome c'. Succinate and NADH reduced the same types of cytochromes. However, a considerable amount of cytochrome b561 with associated beta and gamma bands at 531 and 429 nm, respectively, was reducible by succinate, but not by NADH. A substantial fraction of the membrane-bound b-type cytochrome was non-substrate reducible and was found in dithionite-reduced minus substrate-reduced spectra. Cytochrome c2 may be localized in a branch of the electron transport system, with the branch-point at the level of ubiquinone. The separate pathways rejoined at a common terminal oxidase. Two terminal oxidases with different KCN sensitivity were present in the respiratory chain, one of which was sensitive to low concentrations of KCN and was connected with the cytochrome chain. The other terminal oxidase which was inhibited only by high concentrations of cyanide was located in a branched pathway, through which the electrons could flow from ubiquinone to oxygen bypassing the cytochrome chain.
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PMID:The respiratory electron transport system of heterotrophically-grown Rhodopseudomonas palustris. 16 26

1. 12-(9-Anthroyl)stearic acid can be incorporated into mitochondrial membranes. 2. The fluorescence properties of the membrane-bound probe are different from those of the free molecule. 3. The intensity of emission and fluorescence life-time of the probe is enhanced when, in the presence of substrate, the electron-transport chain is reduced. 4. This change in intensity has been demonstrated to be a result of collisional quenching by oxidised ubiquinone in the oxidised membrane but not when the respiratory chain is in the reduced state. 5. In pulsing anaerobic mitochondria with oxygen the rate of the fluorescence change is found to be slower than the rate of ubiquinone oxidation, suggesting that the probe detects a structural transition in the mitochondrial inner membrane. 6. This transition results in a constraint on ubiquinone motion in the reduced system. Model experiments, using lipid dispersions, have been carried out to test some of the interpretations.
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PMID:12-(9-Anthroyl)stearic acid, a fluorescent probe for the ubiquinone region of the mitochondrial membrane. 17 92

The origin of most of the electron paramagnetic resonances obtained at low temperature and low microwave power from heart tissue and subcellular fractions derived therefrom is now understood. A signal that emerges on partial reduction with characteristic lines at 3227 G (0.3227 tesla) and 3309 G (0.3309 tesla) (at 9.2 GHz) and disappears again on full reduction has remained unidentified. According to its behavior on oxidation-reduction, the substance giving rise to this signal has the properties of a two-electron acceptor. The signal is strongly dependent on temperature and can only be well resolved at less than 20 degrees K. It is readily elicited in submitochondrial particles by partial reduction, but has not been observed in submitochondrial particles from which ubiquinone has been removed by pentane extraction. When ubiquinone is reincorporated into extracted submitochondrial particles, the signal is again easily produced by partial reduction. Electron paramagnetic resonance spectra of partially reduced submitochondrial particles recorded at 34 GHz show lines centered about g approximately 2 with the same separation (approximately 82 G; approximately 0.0082 tesla) as do 9.2 GHz spectra, whereas no lines are detected with a separation of approximately 82 X 34/9.2 G (0.0082 X 34/9.2 tesla). We suggest, on the basis of these observations, that the unidentified signal arises from an interaction of ubisemiquinone and a second paramagnetic species. Three obvious choices exist concerning this second species: ubisemiquinone, flavin semiquinone, or an iorn-sulfur center. It is not possible without much additional information to decide between these possibilities. Since we have never observed the signal in the absence of the membrane-bound, high-potential type iron-sulfur protein, we have considered involvement of this species in the interaction. However, according to computer simulations of the observed electron paramagnetic resonance spectra, which yield best fits for semiquinone-semiquinone interaction, the possibility that ubi- or flavin semiquinone is the interaction partner appears more likely at this time. The interaction appears to be of the magnetic dipole-dipole type, but it is not certain whether there is also a contribution from spin exchange coupling. If it is assumed that the signal is due to magnetic dipole-dipole interaction, the distance of the partners is less than or equal to 7.7 A.
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PMID:Interaction of ubisemiquinone with a paramagnetic component in heart tissue. 17 46

An NADH dehydrogenase possessing a specific activity 3-5 times that of membrane-bound enzyme was obtained by extraction of Acholeplasma laidlawii membranes with 9.0% ethanol at 43 degrees C. This dehydrogenase contained only trace amounts of iron (suggesting an uncoupled respiration), a flavin ratio of 1:2 FAD to FMN and 30-40% lipid. Its resistance to sedimentation is probably due to the high flotation density of the lipids. It efficiently utilized ferricyanide, menadione and dichlorophenol indophenol as electron acceptors, but not O2, ubiquinone Q10 or cytochrome c. Lineweaver-Burk plots of the dehydrogenase were altered to linear functions upon extraction with 9.0% ethanol. A secondary site of ferricyanide reduction could not be explained by the presence of cytochromes, which these membranes lack. In comparison to other respiratory chain-linked NADH dehydrogenases in cytochrome-containing respiratory chains, this dehydrogenase was characterized by similar Km's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, but considerably smaller V's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, and smaller specific activities. It was not stimulated or reactivated by the addition of FAD, FMN, Mg2+, cysteine or membrane lipids, and was less sensitive to respiratory inhibitors than unextracted enzyme. The ineffectiveness of ADP stimulation on O2 uptake, the insensitivity to oligomycin and the very low iron content of A. laidlawii membranes were considered in relation to conservation of energy by these cells. Some kinetic properties of the dehydrogenation, the uniquely high glycolipid content and apparently uncoupled respiration at Site I were noteworthy characteristics of this NADH dehydrogenase from the truncated respiratory chain of A. laidlawii.
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PMID:The reduced nicotinamide adenine dinucleotide "oxidase" of Acholeplasma laidlawii membranes. 17 76

The membrane-bound respiratory system of the gram-negative bacterium Spirillum itersonii was investigated. It contains cytochromes b (558), c (550), and o (558) and beta-dihydro-nicotinamide adenine dinucleotide (NADH) and succinate oxidase activities under all growth conditions. It is also capable of producing D-lactate and alpha-glycerophosphate dehydrogenases when grown with lactate or glycerol as sole carbon source. Membrane-bound malate dehydrogenase was not detectable under any conditions, although there is high activity of soluble nicotinamide adenine dinucleotide: malate dehydrogenase. When grown with oxygen as the sole terminal electron acceptor, approximately 60% of the total b-type cytochrome is present as cytochrome o, whereas only 40% is present as cytochrome o in cells grown with nitrate in the presence of oxygen. Both NADH and succinate oxidase are inhibited by azide, cyanide, antimycin A, and 2-n-heptyl-4-hydroxyquinoline-N-oxidase at low concentrations. The ability of these inhibitors to completely inhibit oxidase activity at low concentrations and their effects upon the aerobic steady-state reduction levels of b- and c-type cytochromes as well as the aerobic steady-state reduction levels obtained with NADH, succinate, and ascorbate-dichlorophenolindophenol suggest that presence of an unbranched respiratory chain in S. itersonii with the order ubiquinone leads to b leads to c leads to c leads to oxygen.
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PMID:Membrane-bound respiratory of Spirillum itersonii. 18 74

Oriented multilayers made from beef heart and yeast mitochondria and submitochondrial particles were studied using electron paramagnetic resonance. EPR signals from membrane-bound iron-sulfur clusters and from a spin-coupled ubiquinone pair are highly orientation dependent, implying that these redox centers are fixed in the membrane at definite angles relative to the membrane plane. Typically the iron-iron axis (gz) of the binuclear iron-sulfur clusters is in the membrane plane. This finding is discussed in terms of the protein structure. The tetranuclear iron-sulfur clusters can have their gz axis either perpendicular or parallel to the membrane plane, but intermediate orientation was not observed.
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PMID:The orientation of iron-sulfur clusters and a spin-coupled ubiquinone pair in the mitochondrial membrane. 22 37

Taking into account the found earlier relation of vitamin E to the ubiquinone functioning and metabolism, the authors studied the enzymic activity of succinate dehydrogenase, NADH-dehydrogenase and cytochrome-c-oxidase--coenzyme Q binding sites of the respiratory chain of the rat liver mitochondria. The experiments were carried out with female rats who received a vitamin-E-deficient diet for 6 months. The enzymic activities and the ubiquinone content in the liver mitochondria of these animals are shown to be considerably lower as compared to the animals received a vitamin E diet; alpha-ocopherol, alpha-tocopheronolactone and ubiquinone 3h after administration manifest a clearly pronounced normalizing effect relative to both the enzymic activity and the ubiquinone content. An assumption is advanced that the effect of alpha-tocopherol and its metabolite is associated with controlling the level of functionally active ubiquinone in the mitochondria. Other mechanisms of the membrane-bound enzymes control by the compounds under study are also discussed in connection with the alpha-tocopherol effect on the mitochondrial membranes.
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PMID:[Activity of certain redox enzymes of rat liver mitochondria at different levels of dietary vitamin E]. 22 6


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