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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bound and solubilized ATPase from Escherichia coli show similar kinetic properties. The saturation curves for MgATP are hyperbolic with both preparations. The straight lines in the Line-weaver-Burk plot indicate that MgATP is the true substrate, that one molecule MgATP is bound per enzyme molecule, and that there is no cooperativity. Presence of EDTA leads to sigmoidal saturation curves. This effect could be reversed by adding MgCl2 stoichiometrically to EDTA. Different results in other publications, especially in that of CARREIRA and MUNOZ1 can be explained as being primarily the consequence of complexing agent contaminations in the assay.
Mol Cell Biochem 1977 Apr 12
PMID:Kinetic properties of soluble adenosine triphosphatase of Escherichia coli. 14 5

The Arrhenius plots for the active and low activity soluble forms of the ATPase purified from the membranes of Micrococcus lysodeikticus grown at 30 degrees C presented discontinuities at 30 and 33 degrees C, respectively. Their activation parameters differed, being highest for the low activity form of the enzyme. Both forms underwent changes in their molecular properties as a consequence of being enzymically active, i.e., upon incubation with substrates at an adequate temperature. These changes consisted of a decrease in the relative mobilities of some of their subunits in dodecyl sulphate polyacrylamide gel electrophoresis, and the temperature at which they occurred depended on the energy of activation of the particular form of the ATPase used. The low activity form required an incubation temperature of 50 degrees C, whereas for an active form 37 degrees C was sufficient.
Mol Cell Biochem 1977 Aug 19
PMID:Activation parameters and molecular changes induced by substrate hydrolysis of the adenosine triphosphatase of Micrococcus lysodeikticus. A comparison of three different soluble forms of the enzyme. 14

The extranuclear mitochondrial oligomycin-resistant mutation of Aspergillus nidulans, (oliA1), was transferred asexually into four nuclear oligomycin-resistant strains of different phenotypes. In all four cases, the possession of the nuclear plus extranuclear mutation led to an increase in the in vivo level of oligomycin resistance. In two cases, the altered cytochrome spectrum and impaired growth ability determined by (oliA1) were suppressed by the nuclear mutations. In the third case, the in vitro oligomycin resistance of the double mutant ATPase was dramatically increased above that of either of the component single mutant strains, indicating a synergystic interaction between the nuclear and extranuclear gene products. In the fourth case, the double mutant became cold-sensitive. A new extranuclear mitochondrial oligomycin-resistant mutation (oliB332) is described. This mutant is phenotypically similar to, though not identical with, (oliA1) but is separable by recombination. A range of nuclear oligomycin-resistant mutants have been mapped. Despite presenting five distinctly different phenotypes, they all map at the same locus.
Mol Gen Genet 1977 Sep 09
PMID:Nuclear-extranuclear interactions affecting oligomycin resistance in Aspergillus nidulans. 14 64

The effects of diamide were studied in rat kidney cortical tissue. It was found that diamide increased oxidized glutathione levels and inhibited Na+-K+-ATPase activity. Consistent with this finding was the observation that diamide compromised the sodium gradients maintained in renal cortical slices. Amino acid transport studies with ouabain or a sodium-free buffer indicated that diamide interferes with both Na+-dependent and Na+-independent transport systems. These results indicate that diamide has a number of different effects on renal cortical tissue and emphasize the important role of glutathione in maintaining control of a number of key metabolic pathways.
Mol Cell Biochem 1977 Dec 29
PMID:The role of glutathione in renal cortical tissue. Effects of diamide on Na+ and GSSG levels, amino acid transport and Na+-K+-ATPase activity. 14 23

Soluble, oligomycin-insensitive ATPase released from beef heart mitchondria by chloroform extraction can be further purified by Sepharose 6B gel filtration. This purification increases enzyme activity 4--5 times (100-130U/mg). According to specific activity, high purity and ability to reconstitute oligomycin-sensitive complex, isolated ATPase is quite comparable with enzyme preparations isolated by other methods.
Mol Cell Biochem 1977 Dec 29
PMID:Purification and properties of adenosine triphosphatase solubilized from beef heart mitochondria by chloroform. 14 24

A method for primary culture of ovine myometrial cells is described. After dissection, myometrium of ewe uteri was digested in trypsin and collagenase. The cells were preplated for 1 h at 37 degrees C. The non-attached cells were grown in appropriate medium supplemented with 2% fetal calf serum. They had a doubling time of 3 days, reached confluency at 10 days and did not exhibit contact inhibition. Cultures were maintained up to 22 days. Characterization of the cells was achieved by electron microscopy, analysis of myosin in cell extracts and assessment of hormone sensitivity. The cells were found to contain myofilaments, characteristic of smooth muscle. A high content of myosin (6--13%) was demonstrated on SDS-polyacrylamide gel electrophoresis: this was confirmed by ATPase activity assay. Cells responded to estradiol stimulation by increased protein synthesis, and bound [3H]estradiol in a specific and saturable way. These results suggest that myometrial cells grown in primary culture should provide a useful model for studying the hormonal control of contractile protein synthesis.
Mol Cell Endocrinol 1978 Oct
PMID:Myometrial cells in primary culture: characterization and hormonal profile. 15 21

1. The distribution of ATPase and several marker enzymes was examined after differential and sucrose gradient centrifugation of yeast homogenates. 2. An ATPase activity not sensitive to oligomycin is found exclusively associated with a particulate fraction equilibrating at densities of 1.23-1.25. This particulate material shows the chemical and enzymatic characteristics of the yeast plasma membrane. 3. The pH optimum of the plasma membrane ATPase is 5.6, as compared with 8.5 for the mitochondrial ATPase. In addition to oligomycin, the enzyme is not sensitive to other inhibitors of the mitochondrial ATPase as azide, dicyclohexylcarbodiimide and the mitochondrial ATPase inhibitor protein. It is inhibited by p-chloromercuryphenyl sulfonate, fluoride, quercetin and by the antibiotic Dio-9 but is not affected by ouabain. 4. The plasma membrane ATPase shows a high affinity for ATP (Km = 0.1 mM) and is very specific for this compound, hydrolyzing other nucleotide triphosphates less than 25% as rapidly. No activity was detected with ADP. 5. The enzyme requires a divalent cation for activity and Mg2+ is the most effective. It is not significantly stimulated by K+ or bicarbonate and Ca2+ is inhibitory. 6. The activity cannot be assayed in intact cells unless they are permeabilized with toluene. This suggest that the active site is on the cytoplasmic side of the plasma membrane.
Mol Cell Biochem 1978 Nov 30
PMID:Characterization of the plasma membrane ATPase of Saccharomyces cerevisiae. 15 59

The phospholipid requirement of membrane-bound enzymes may depend on several reasons. In our laboratory we have investigated lipids (1) as a bidimensional medium required for the movement of Coenzyme Q, a lipid-soluble cofactor of the mitochondrial respiratory chain, and (2) as a hydrophobic environment necessary to impose the proper conformation to membrane-bound enzymic proteins. We have found that Coenzyme Q, once reduced by NADH dehydrogenase, must cross the inner mitochondrial membrane; only quinones having long isoprenoid side chains can easily cross phospholipid bilayers, and this is the reason why a short chain quinone such as CoQ-3 inhibits NADH oxidation. The incapability of short quinones to cross lipid bilayers is due to their disposition in the lipid bilayer, stacked within the phospholipids. The conformational role of lipids has been investigated indirectly observing the kinetics of membrane-bound enzymes, e.g. the mitochondrial ATPase, and directly by circular dichroism. Lipid removal or lipid perturbation with organic solvents induce a decrease of alpha-helical content in mitochondrial proteins, and give rise to a series of kinetic changes in ATPase, including uncompetitive inhibition, increased activation energy, and loss of cooperativity in oligomycin inhibition. The recognition of a conformational role of lipids has allowed us to postulate a working hypothesis for the mechanism of action of general anesthetics. Such drugs have been found by us, by means of spin labels and fluorescent probes, to disrupt lipid protein interactions in several membranes, including synaptic membranes. The loosening of such interactions is believed to induce conformational changes, which will alter ion transport systems necessary to the propagation of neural impulses. Conformational changes induced by anesthetics have been found by us both directly by circular dichroism and indirectly by enzyme kinetics. The conformational effect of anesthetics is not directly exerted on the proteins but is mediated through the lipids. In agreement with this hypothesis we have found that membrane-bound acetylcholinesterase is inhibited by anesthetics, whereas the solubilized enzyme is not inhibited. However, binding of the solubilized enzyme to phospholipids restores anesthetic inhibition.
Mol Cell Biochem 1978 Nov 30
PMID:Biophysical studies on agents affecting the state of membrane lipids: biochemical and pharmacological implications. 15 58

With a view towards identifying new ATPase loci on the mitochondrial genome a large number of oligomycin-, ossamycin- and venturicidin-resistant mutants were isolated after MnCl2 mutagenesis. The mutants were subjected to mass-screens which divided them into different cross-resistance phenotype-classes and also distinguished the common OLI1 mutations from the mutations at all other loci. Allelism tests between examples of the different classes of phenotype indicated that the majority of mutations in the population mapped at the previously known loci OLI1, OLI2, OLI3, and OLI4. Mutations conferring specific ossamycin resistance defined two new loci, namely OSS1 and OSS2 which are linked to the OLI2 and OLI1 loci respectively. A few rare mutations comprise a new locus OLI5 which is linked to the OLI1 locus (12.6% total recombination). In conclusion we can now say that that there are two unlinked segments of the mitochondrial genome, each of which is composed of several distinct, genetically-linked loci. One segment contains the OLI1, OLI3, OLI5 and OSS2 loci and the other the OLI2, OLI4 and OSS1 loci. The phenotypically-distinguishable mutations described herein should facilitate fine-structure mapping of these two segments.
Mol Gen Genet 1979 Oct 03
PMID:Genetics of oxidative phosphorylation: mitochondrial loci determining ossamycin-, venturicidin- and oligomycin-resistance in yeast. 16 Sep 74

Considerable progress has been made in recent years in our understanding of the phosphorylating apparatus in mitochondria, chloroplasts, and bacteria. It has become clear that the structure and the function of the ATP synthesizing apparatus in these widely divergent organisms is similar if not virtually identical. The subunit composition of F1, its molecular architecture, the location and function of substrate binding sites, as well as putative control sites, understanding of the component parts of the oligomycin-sensitive ATPase complex, and the role of these components in the function of the complex all are under active investigation in many laboratories. The developing information and the new insights provided have begun to permit experimental approaches, at the molecular level, to the mode of action of the ATPase in electron-transport-coupled ATP synthesis.
Adv Enzymol Relat Areas Mol Biol 1979
PMID:Mitochondrial ATPase. 16 56


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