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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied qualitative and quantitative changes of several parameters during chloroplast development in Spirodela oligorhiza (duckweed). On a dry weight basis, the amount of protein increases from 2.5% (w/w) in dark-grown to 7.8% (w/w) in light-grown fronds. At the same time the amount of starch drops from 50% to 27% (w/w). Using an immunochemical quantification method we have found that during greening of etiolated plants the amount of all subunits of the ATPase complex per frond increases 10-fold, whereas the level of the subunits of ribulose-1,5-biphosphate carboxylase increases 50-fold. Cytochrome f was found to be present in dark-grown Spirodela and the amount of this polypeptide per frond increases about 30-fold. The concentration of a polypeptide that possibly represents a cytochrome b6 subunit increases about 10-fold upon greening. The molar ratio of the CF1-beta and CF1-gamma subunits of the ATPase complex varies over 2-3, while in all stages of chloroplast development studied the molar ratio of the carboxylase subunits is about 1. As these values are in agreement with the stoichiometrical amounts in the native protein complexes, we conclude that the synthesis of CF1-beta and CF1-gamma, as well as the synthesis of the large and small carboxylase subunits, are strictly coordinated during chloroplast biogenesis in Spirodela oligorhiza.
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PMID:Protein synthesis during chloroplast development in Spirodela oligorhiza. Coordinated synthesis of chloroplast-encoded and nuclear-encoded subunits of ATPase and ribulose-1,5-bisphosphate carboxylase. 622 4

Two classes of tributyltin (TBT) resistant, spontaneous mutants of Escherichia coli K-12 were isolated, using a cytochrome containing (W 1485) and a cytochrome deficient ( SASX76 ) strain. In contrast to the cytochrome sufficient strain, the cytochrome deficient strain was found to be fifty times more sensitive to TBT. The class I mutants, isolated from strain W 1485, also showed cross-resistance to triphenyltin (TPT). As compared to its wild type parent, the TBT-resistant mutants exhibited mucoid colony type, aberrant cell morphology and reduced uptake of TPT. Based on these results, it was suggested that the resistance of class I mutants to TBT may be associated with above mentioned alterations. The class II TBT-resistant mutants were isolated from the cytochrome deficient strain, SASX76 . In comparison to class I mutants, these class II mutants were found to have TBT-resistant membrane bound adenosine triphosphatase (ATPase) which may account for their resistance to TBT.
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PMID:Isolation and characterization of tributyltin resistant mutants of Escherichia coli. 623 3

The reduction of CO2 or any other methanogenic substrate to methane serves the same function as the reduction of oxygen, nitrate or sulfate to more reduced products. These exergonic reactions are coupled to the production of usable energy generated through a charge separation and a protonmotive-force-driven ATPase. For the understanding of how methanogens derive energy from C-1 unit reduction one must study the biochemistry of the chemical reactions involved and how these are coupled to the production of a charge separation and subsequent electron transport phosphorylation. Data on methanogenesis by a variety of organisms indicates ubiquitous use of CH3-S-CoM as the final electron acceptor in the production of methane through the methyl CoM reductase and of 5-deazaflavin as a primary source of reducing equivalents. Three known enzymes serve as catalysts in the production of reduced 5-deazaflavin: hydrogenase, formate dehydrogenase and CO dehydrogenase. All three are potential candidates for proton pumps. In the organisms that must oxidize some of their substrate to obtain electrons for the reduction of another portion of the substrate to methane (e.g., those using formate, methanol or acetate), the latter two enzymes may operate in the oxidizing direction. CO2 is the most frequent substrate for methanogenesis but is the only substrate that obligately requires the presence of H2 and hydrogenase. Growth on methanol requires a B12-containing methanol-CoM methyl transferase and does not necessarily need any other methanogenic enzymes besides the methyl-CoM reductase system when hydrogenase is present. When bacteria grow on methanol alone it is not yet clear if they get their reducing equivalents from a reversal of methanogenic enzymes, thus oxidizing methyl groups to CO2. An alternative (since these and acetate-catabolizing methanogens possess cytochrome b) is electron transport and possible proton pumping via a cytochrome-containing electron transport chain. Several of the actual components of the methanogenic pathway from CO2 have been characterized. Methanofuran is apparently the first carbon-carrying cofactor in the pathway, forming carboxy-methanofuran. Formyl-FAF or formyl-methanopterin (YFC, a very rapidly labelled compound during 14C pulse labeling) has been implicated as an obligate intermediate in methanogenesis, since methanopterin or FAF is an essential component of the carbon dioxide reducing factor in dialyzed extract methanogenesis. FAF also carries the carbon at the methylene and methyl oxidation levels.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The bioenergetics of methanogenesis. 623 47

The effects of the mitochondrial protein synthesis inhibitor chloramphenicol and the mitochondrial F0 adenosine triphosphatase inhibitor oligomycin on the synthesis of nucleus-encoded cytochrome c protein were studied. Both inhibitors stimulated cytochrome c protein synthesis in the derepressed state (growth in media containing 2% raffinose) but had no effect on the synthesis of the cytochrome c protein in the repressed state (growth in media containing 5% glucose). Oligomycin uncoupled the synthesis of the apoprotein from its processing into the hemoprotein. Neither antibiotic had a significant effect on the rate of glucose repression of cytochrome protein synthesis. The kinetics of cytochrome c derepression and the effects of these two antibiotics on these kinetics were also studied. Cells were derepressed by transfer from glucose- to faffinose-containing media, and the rate of cytochrome c synthesis increased from the repressed to the derepressed level during the second hour of derepression. Chloramphenicol delayed this derepression, but after 5 h the rate of cytochrome c protein synthesis increased to twice the rate of synthesis in uninhibited cells. On the other hand, oligomycin inhibited derepression of cytochrome c. These results are discussed with respect to the effects of mitochondrial function in the derepressed and repressed states and during the processes of repression and derepression of cytochrome c.
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PMID:Effect of mitochondrial functions on synthesis of yeast cytochrome c. 624 23

Analyses of plasma membrane and other subcellular fractions indicate that the primary location of cytochrome b in human neutrophils is not the plasma membrane. The procedure developed for the purification of plasma membrane from fresh human neutrophils yielded a 14-fold enrichment in the marker enzyme 5'-nucleotidase and a 10-fold enrichment in ouabain-sensitive ATPase. On sucrose density gradients, the peak density of 5'-nucleotidase activity was 1.12 g/ml, and was shifted after digitonin addition to 1.15 g/ml. Protein in the plasma membrane equalled approximately 8 percent of the whole cell protein. A b-type cytochrome was found to be present in the plasma membrane fraction at a concentration of 205 pmol/mg of protein, which is three times greater than that in the neutrophil overall. Although this cytochrome has been reported previously in the neutrophil, this is the first determination for purified plasma membrane and may indicate that b-type cytochrome has a dual localization in the human neutrophil. Differential centrifugation results suggest that the primary location is in the granules, probably specific granules. Quinone content in the plasma membrane was found to be 740 pmol/mg of protein, a concentration two times greater than in the whole cell. Such a small enhancement of quinone indicates that quinone also is not primarily located in the plasma membrane.
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PMID:Isolation of plasma membrane from human neutrophils and determination of cytochrome b and quinone content. 626 84

Rats were coexposed to lead (Pb) and Copper (Cu) through drinking water and intraperitoneally, respectively, for a period of 21 days. Neurochemical studies in these rats showed significant reduction in the activity of adenosine triphosphatase, cytochrome-c-oxidase, diaphorase and in the levels of biogenic amines in the rats simultaneously exposed to the two metals compared to either of the metal alone. These neurotoxic effects were not related to the contents of either of the metals in the brain since their accumulation after combined exposure was much less than observed after individual exposure to Pb or Cu.
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PMID:Neurochemical changes in rats coexposed to lead and copper. 628 90

Semm's technique of endocoagulation has been used by the authors for haemostasis in endoscopic abdominal surgery at the Department of Gynecology and Obstetrics, University of Kiel since 1973. --Enzyme-histochemical and histological tests, all based on endocoagulation or high-frequency current procedures, were applied to 100 human fallopian tubes. Fifteen of them remained uncoagulated and were used for comparison. --Membrane ATPase, 5-nucleotidase, cytochrome-C-oxydase, and other essential enzymes in cellular metabolism were inactivated by temperatures in excess of 57 degrees C. These enzymes, consequently, were no longer detectable from enzyme-histochemical preparations, whereas active tissue regions, those which still contained vital cells, were stained black to brown. --Negative enzyme reactions occurred in response to a coagulation forceps temperature of 120 degrees C, when applied not less than 20 seconds. Residual enzyme activities were still recordable from certain tubal areas, when forceps temperatures below 120 degrees C had been used. In such cases coagulation was insufficient, particularly in the inner layers of tubes (epithelium, mucosa). Temperatures above 130 degrees C and coagulation lengths of more than 20 seconds proved to be unnecessary, since no improvement in results was thus achievable. Temperatures of 140 degrees C and more have changed coagulated tissue into "adhesive" and make it stick to the coagulation forceps. Instrument withdrawal can in such cases cause bleeding rather than the desired haemostatic effect.
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PMID:[Devitalization and haemostasis by thermal destruction--results of enzyme-histochemical and histological examination of oviduct specimens, following tissue coagulation by means of endocoagulation or high-frequency current (author's transl)]. 628 61

Rough microsomes from rat liver of both control and methylcholanthrene-treated animals were subfractionated on a discontinuous sucrose gradient into three fractions according the their sedimentation velocity. The slowly sedimenting vesicles were enriched in electron transport enzymes, while those in the pellet showed higher phosphatase and ATPase activities. Methylcholanthrene treatment introduced typical changes in enzyme composition, mainly an increase of the cytochrome P-448. The individual phospholipids exhibited an identical distribution pattern in the three subfractions and no change occurred after induction with methylcholanthrene treatment. Nearest neighbour analysis of phosphatidylethanolamine with dinitrodifluorobenzene revealed a similar pattern in the enzymatically different subfraction, that is, no cross-linking with phosphatidylserine occurred. One-third of the phosphatidylethanolamine was in monomer and dimer form and about two-thirds was protein linked. When membrane and enzyme synthesis was induced, cross-linking to proteins were substantially decreased. The experiments indicate that the phospholipids are distributed in a homogenous fashion in the lateral plane of the rough microsomal membrane and do not support the possibility that phosphatidylethanolamine is specifically associated with cytochrome P-450.
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PMID:Phospholipid and enzyme arrangements of rat liver rough microsomal subfractions from control and methylcholanthrene-treated animals. 628 90

Baker's yeast mitochondrial cytochrome b-564 is characterized by exhibiting both a labile pH-independent high-potential form (E'o, pH 7 = + 190 mV) and a stable pH-dependent (pKa = 6.8) low-potential form (E'o, pH 7 = + 70 mV). The different behavior of these two forms of cytochrome b-564 versus pH seems to be a decisive factor for transduction of redox energy into acid-base energy in oxidative phosphorylation site 2. Deenergizing treatments, such as ADP plus Pi, result in the conversion of all the mitochondrial cytochrome b-564 into its low-potential form, whereas energization with ATP specifically transforms the cytochrome into its high-potential form, the ATP effect being neutralized by the ATPase inhibitor oligomycin and by the uncoupler FCCP. Accordingly, a minimal model for coupling between redox energy and acid-base energy through an electronically energized and protonated ferricytochrome b-564 intermediate is proposed. The energy-transducing properties of mitochondrial cytochrome b-564 seems to be shared by chloroplast cytochrome b-559.
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PMID:Coupling between redox and acid-base energy by cytochrome b-564 in Baker's yeast mitochondria. 639 82

An investigation was performed of the liver mitochondrial respiratory function in rats after 1, 3 and 6 weeks of biliary obstruction and the following results were obtained: 1) Various parameters of liver mitochondrial respiratory function, such as respiratory control ratio, ADP/O, O2 consumption in state 3 respiration and adenosine triphosphate synthesis were found to decrease with prolongation of biliary obstruction. 2) The mitochondrial respiratory enzymes, cytochrome a (+a3) and cytochrome c(+c1) showed that both decreased in contents with prolongation of obstruction, particularly the latter. 3) The activation ratio of ATPase (latent ATPase/dinitrophenol stimulated ATPase) was increased after long term biliary obstruction, which was thought to indicate the severe damage of mitochondrial membrane. 4) Investigation of the respiratory function with the various respiratory substrates showed that the locations of mitochondrial respiratory inhibition in obstructive jaundice are at sites 1 and 2, which is the same as the situation seen in nonspecific damage of mitochondria. 5) There was a high degree of mitochondrial respiratory disturbance by bile acids, particularly CDCA, which is thought to be one of the causal factors of liver dysfunction in obstructive jaundice. 6) Mitochondrial respiratory function was markedly disturbed in hypotension, and the degree of which correlated with length of time of biliary obstruction.
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PMID:Mitochondrial function of rat liver in biliary obstruction. 644 87


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