Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Controlled tryptic digestion of purified rat skeletal muscle sarcoplasmic reticulum (Ca2+ + Mg2+)-adenosine triphosphate yields two products designated Fragments 3a and 3b with molecular weights of 65,000 and 56,000 respectively. The isolation of these products in high yield should facilitate exploration of the molecular characteristics of this adenosine triphosphatase. A simple, rapid method for accomplishing this isolation was developed which provides a high yield and utilizes mild conditions. The fragments obtained by this method were used to determine the phospholipid and sulfhydryl contents of Fragments 3a and 3b. In addition, information was obtained on the orientation of these adenosine triphosphatase components in the enzyme lipoprotein complex.
Mol Cell Biochem 1978 Feb 24
PMID:Isolation of subunits from trypsin-cleaved sarcoplasmic reticulum Ca2+ transport adenosine triphosphatase. 14 1

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

Recent studies on the interactions of soluble proteins, membrane proteins and enzymes with phospholipid model membranes are reviewed. Similarities between the properties of such systems and the behavior of biomembranes, such as alterations in the redox potential of cytochrome c after binding to membranes and effects of phospholipid fluidity on (Na+K) ATPase activity, are emphasized. The degree of correspondence between the behavior of model systems and natural membranes encourages the continuing use of model membranes in studies on protein-lipid interactions. However, some of the data on the increase of surface pressure of phospholipid monolayers by proteins and increases in the permeability of liposomes indicate that many soluble proteins also have a capability to interact hydrophobically with phospholipids. Thus a sharp distinction between both peripheral and integral membrane proteins and non-membrane proteins are not seen by these techniques. Cautious use of such studies, however, should lead to greater understanding of the molecular basis of cell membrane structure and function in normal and pathological states. Studies implicating protein-lipid interactions and (Na+K) ATPase activity in membrane alterations in disease states are also briefly discussed.
Mol Cell Biochem 1976 Feb 25
PMID:Protein-liposome interactions and their relevance to the structure and function of cell membranes. 17 56

The interactions between the mitochondrial and nucleocytoplasmic systems required for mitochondriogenesis have been investigated at several different levels. Those involved in the formation of functional enzyme complexes have been studied using cytochrome oxidase: this multimeric (2 X 7 and 2 X 6 subunits for enzymes from yeast and beef heart respectively) has been resolved, and the mitochondrial contribution has been shown to be dispensible for catalytic function proper. Using novel mutants, with a mitochondrial mode of inheritance, a mitochondrial gene product localized in the oligomycin-sensitive ATPase has been implicated in the assembly not only of this complex, but of cytochrome oxidase as well. Interactions required for the genetic competence of the mitochondrial system have become apparent as a result of studies in the mechanism of action of the highly effective mitochondrial mutagen ethidium bromide. This agent first becomes covalently inserted into mitochondrial DNA and, after its excision, eventually results in extensive degradation of the macromolecule. The excision reaction has now been shown to be performed by a complex between the oligomycin-sensitive ATPase and a DNA-binding protein presumably involved in recognizing the damage. On the level of replication and expression of the mitochondrial genome studies using thermolabile mutants have demonstrated that these processes appear independent of the replication of nuclear DNA but not of its expression.
Mol Cell Biochem 1977 Feb 04
PMID:Integration and regulation of mitochondrial assembly in yeast. 19 97

1. The mechanism underlying the raised leucocyte sodium content in fulminant hepatic failure was studied by measurement of sodium fluxes, (Na+ + K+)-dependent adenosine triphosphatase activity, and leucocyte ATP content. 2. The rate constant for sodium efflux in the leucocytes was significantly reduced, and attributable to reduced activity of the enzyme (Na+ + K+)-ATPase. Leucocyte ATP content was not significantly different from that of control cells. 3. Incubation of cells from patients in the sera of normal subjects resulted in a reversal of these changes. Inhibition of the leucocyte sodium efflux rate constants and (Na+ +K+)-ATPase of normal cells was achieved by incubation in sera from patients. 4. We suggest that the raised sodium content of leucocytes in fulminant hepatic failure is attributable to a defective sodium pumping mechanism, possibly due to a circulating toxin.
Clin Sci Mol Med 1978 Oct
PMID:A study in vitro of the sodium pump in fulminant hepatic failure. 21 31

A generalized scheme of the reaction pathways during activation of the Na,K-ATPase by sodium and potassium ions and a relevant molecular model of the Na-pump are proposed. The model suggests light and heavy enzyme subunits possessing cavities with ion exchange sites. The cavities are of limited size and can contain only 3 sodium or 2 potassium ions. Free energy of ATP hydrolysis is expended on the formation of a special transient nonequilibrium enzyme conformation. In this conformation ion exchange between the subunit cavities becames possible. Na-pump operates as an enthropy machine: the ion movement across the membrane is provided by thermal oscillations of the subunits.
Mol Biol (Mosk)
PMID:[Mechanism of coupling of ion transport and ATP hydrolysis in the Na-pump]. 22 May 23


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