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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present studies concern the roles of synthesis and degradation of the large subunit of (Na+ + k+)-adenosine triphosphatase (NaK-ATPase) in the response to triiodothyronin (T3). Single doses of either the diluent of T3 (50 mug/100 g body weight) were given to two pairs of surgically thyroidectomized rats. Twenty hours after injection, the rats received 3H- or 35S-labeled methionine administered as a constant injusion into the tail vein for 1 h. The kidneys were removed either 8 h or 20 h after infusion and the eight kidneys were divided into pairs, as follows. I, 3H (diluent)/35S (T3); II, 35S (diluent)/3H (T3); III, 3H (diluent)/35S (diluent); IV, 3H (T3)/35S (T3). Partially purified NaK-ATPase was prepared from the pooled homogenates and prepared from the pooled homogenates and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAG-electrophoresis). The large subunit of NaK-ATPase was identified by (Na+ + mg2+)-dependent and K+-sensitive incorpotation of 32P from [gamma-32P]ATP. This component had an estimated molecular weight of 92,000 and migrated as a single peptide in gels of varying total carylamide concentration, with respect to: (1) Coomassie blue staining, (b) (Na+ + Mg2+)-dependent, K+-sensitive incorporation of 32P from [gamma-32-P]ATP, and (c) T3-dependent enhanced incorporation of labeled methionine. T3 augmented incorporation of labeled methionine into the large subunit by 44% 8 h after infusion of the amino acid and by 61% 20 h after infusion. Incorporation of methionine into two adjacent polypeptides in the SDS gels was unaffected by thyroid status. The effect otical NaK-ATPase was assessed by a double label technique. Pairs of thyroidectomized rats were injected with either the diluent or 50 mug of T3/100 g body weight at 48-h after the first injection (diluent or T3, i.e. Day "zero"). Kidney cortices were processed on either Day 4 or Day 6; the partially purified NaK-ATPase fraction was prepared, labeled with [gamma-32P]ATP, and analyzed by SDS-PAG-electrophoresis. The degredation rate constants of the large subunit were similar; 0.145 and 0.124 day-1 for the hypothyroid and T3-treated groups, respectively. Thus, the T2-dependent increase in incorporation of labeled methionine into the large subunit appears to result from enhanced synthesis and this increase is sufficient to account for the entire increase in both the number of the activity of the NaK-ATPase units.
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PMID:Effect of triiodothyronine on the synthesis and degradation of renal cortical (Na+ + k+)-adenosine triphosphatase. 13 43

A series of group specific reagents has been examined for their ability to inactivate Micrococcus lysodeikticus adenosine triphosphatase assayed with Mg2+ as activating divalent cation. The enzyme activity was not inhibited by sulphydryl, carboxyl, histidine, arginine and methionine specific reagents at inhibitor concentrations below 2 mM. However, the ATPase was inactivated by its chemical reaction with either one molecule of trinitrobenzenesulfonic acid or tetranitromethane, or two to four molecules of N-bromosuccinimide. These results suggest that at least one amino group, one tyrosine and two to four tryptophans are involved in the Mg2+-dependent binding or hydrolysis of ATP.
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PMID:Effect of group specific reagents on the Mg2 +/- dependent activity of purified Micrococcus lysodeikticus ATPase. 72 31

The ATP-energy transducing system in membranes of Escherichia coli is inhibited by dicyclohexylcarbodiimide. The protein component of this complex with which carbodiimides covalently react to inhibit function was previously identified by labeling wild type and dicyclohexylcarbodiimide-resistant mutants with dicyclohexyl[14C]carbodiimide (Fillingame, R. H. (1975) J. Bacteriol. 124, 870-883). This specific carbodiimide-reactive protein has now been purified. The protein was extracted from the membrane with chloroform:methanol and chromatographed on DEAE-cellulose and hydroxypropyl Spehadex G-50 in this sulvent mixture. The resultant 700-fold purification yielded a protein that was homogeneous on dodecyl sulfate-acrylamide gel electrophoresis and virtually free of phospholipid. It remained soluble in neutral chloroform:methanol throughout the purification procedure. The amino acid composition of the purified protein was extraordinary in that only 16% of the amino acids present could be considered polar. Histidine, serine, cysteine, and tryptophan were not found. Abnormally high contents of methionine, glycine, alanine, and leucine were present. One mole of lysine and threonine were found/mole of dicyclohexyl[14C]carbodiimide bound. The minimum molecular weight based on the amino acid composition was 8400. The specific carbodiimide-reactive protein has also been purified without prior modification by dicyclohexylcarbodiimide. The unmodified protein eluted from DEAE-cellulose at a higher salt concentration than the dicyclohexylcarbodiimide-modified form, which suggested that the reaction with the carbodiimide neutralized the negative charge. Only one-third of the total carbodiimide-reactive protein in the membrane was modified by dicyclohexylcarbodiimide under conditions which maximally inhibited adenosine triphosphatase activity. These results rais the possibility that the carbodiimide-reactive protein may be present as an oligomer in the energy-transducing complex. The purification of the unmodified carbodiimide-reactive protein should permit assessment of tis biological function, particularly its role in the protein-translocation process that is catalyzed by this energy-transducing complex.
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PMID:Purification of the carbodiimide-reactive protein component of the ATP energy-transducing system of Escherichia coli. 78 71

The major biological functions of S-adenosyl-L-methionine (SAMe) include methylation of various molecules (transmethylation) and synthesis of cysteine (trans-sulphuration). A stable double salt of SAMe has been found to be effective in intrahepatic cholestasis. The mechanism of its therapeutic effect is not fully understood but presumably involves methylation of phospholipids. Methylation of plasma membrane lipids may affect membrane fluidity and viscosity, which modulate the activities of a number of membrane-associated enzymes, for example, the activity of enzymes involved in Na+/Ca++ exchange (e.g. sarcolemmal vesicles), Na+/K+ adenosine triphosphatase (ATPase) [e.g. hepatocyte plasma membranes], and Na+/H+ exchange (e.g. plasma membranes of colonic cells). Recently, patients with cirrhosis were shown to have an acquired metabolic block in the hepatic conversion of methionine to SAMe. These patients, when administered conventional elemental diets, develop abnormally low plasma concentrations of cysteine and choline, 2 nonessential nutrients present in low concentrations in most elemental diets. These low concentrations probably reflect systemic deficiencies attributable to reduced endogenous syntheses of cysteine and choline caused by limited availability of hepatic SAMe. Such cirrhotic patients are often in negative nitrogen balance and have abnormal hepatic functions, which are corrected by cysteine and choline supplements. Noncirrhotic patients on parenteral elemental diets also become deficient in cysteine and choline. Consequently, these patients may require SAMe as an essential nutrient to normalise their overall hepatic transmethylation and trans-sulphuration activities.
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PMID:Biochemistry and pharmacology of S-adenosyl-L-methionine and rationale for its use in liver disease. 208 85

The effect of vitamin A deficiency on the intestinal absorption of nutrients and the activities of brush border enzymes were studied in albino rats. Intestinal uptakes of D-glucose, L-methionine, L-tryptophan and L-histidine were significantly greater in vitamin A-deficient animals than in controls. The specific activities of total adenosine triphosphatase (ATPase), ouabain-sensitive ATPase, maltase and sucrase in the intestinal mucosa of vitamin A-deprived rats were 121, 124, 131 and 134 per cent respectively, of the corresponding values in control animals. The DNA content of the small intestine in vitamin A-deficient rats was 36.5 per cent lower than in control rats. The stimulation in digestive and absorptive capacity appears to be an adaptive change in vitamin A-deficiency which decreases the intestinal cell population.
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PMID:Effect of vitamin A deficiency on rat intestinal digestive & absorptive functions. 253 19

Ribonucleic acid was isolated from the fundic gastric mucosae of rats and rabbits by cesium chloride centrifugation of guanidine isothiocyanate-denatured mucosal homogenates, and poly A+ RNA was recovered from the pellets by oligodeoxythymidine column selection. When added to rabbit reticulocyte lysates, this poly A+ RNA stimulated [35S]methionine incorporation into trichloroacetic acid-precipitable material. Fluorographic analysis of the lysates showed protein synthesis to be dominated by polypeptides with molecular weights from 40,000 to 50,000, presumably prepepsinogen isoforms. Immune precipitation of the lysates with monoclonal antibodies directed against the gastric H+,K+-adenosine triphosphatase yielded bands at 94 kilodaltons and more diffuse banding at 180 kilodaltons. Further purification of the poly A+ RNA on sucrose gradients eliminated prepepsinogen messenger RNA; nascent H+,K+-adenosine triphosphatase synthesized by purified messenger RNA consisted of polypeptides with molecular weights between 88,000 and 94,000. The study indicates that cell-free translation of gastric mucosal messenger RNA may provide a useful model for analysis of gastric H+,K+-adenosine triphosphatase biosynthesis and processing.
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PMID:Cell-free synthesis of rat and rabbit gastric proton pump. 255 Mar 9

The effects of opioids and of naloxone on ouabain-sensitive Na+,K+-adenosine triphosphatase (ATPase) activity were studied in vitro on membrane fractions from frog spinal cords. The addition of morphine and of the stable enkephalin analogue, D-Ala2,D-Leu5-enkephalin, in concentrations from 10(-7) to 10(-4) M significantly increased Na+,K+-ATPase activity. No effect was found with methionine enkephalin (Met-Enk). However, the addition of two peptidase inhibitors, captopril and phosphoramidon (10(-5) M each), significantly increased Na+,K+-ATPase activity. A further increase in enzyme activity was found when Met-Enk (10(-4) or 10(-7) M) was added simultaneously with peptidase inhibitors. On the other hand, the addition of the opiate antagonist, naloxone, at low concentration (10(-7) M) decreased the activity of Na+,K+-ATPase. These results are discussed with respect to the effect of synthetic and endogenous opioids on the activity of Na+,K+-ATPase.
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PMID:The effect of opioids and of naloxone on Na+,K+-adenosine triphosphatase activity in frog spinal cord membrane fractions. 299 69

The inhibition of glycolysis in tumor cells by methionine requires that the cells be incubated with methionine for several hours in the presence of serum. We now show that in the case of confluent rat-1 fibroblasts transfected with the ras gene the serum can be substituted by insulin and insulin-like growth factor I or II. No other growth factor tested was effective. In subconfluent ras cells additional growth factors (transferrin and high density lipoproteins) were required for maximal inhibition of glycolysis by methionine. Exploration of the mechanism of action of methionine revealed that the accumulation of [35S]methionine into rat-1 fibroblasts was only marginally increased by insulin. We propose that methionine inhibits an adenosine triphosphatase activity because addition of low concentrations of Nonidet P-40 greatly enhanced glycolysis even in the presence of methionine, suggesting that it did not affect the glycolytic enzymes directly. Methionine also affected growth both in monolayer and soft agar. Rat-1 fibroblasts transfected with the ras gene were markedly more sensitive to methionine than cells transfected with the myc gene.
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PMID:Effect of growth factors and methionine on glycolysis and methionine transport in rat fibroblasts and fibroblasts transfected with myc and ras genes. 308 Dec 58

There are alterations in the proteins synthesized during different stages of development of Schistosoma mansoni. The protein profiles at different stages were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When stained by Coomassie blue, no significant differences were seen in protein profiles derived from cultured schistosomula from Days 0 to 6 and from adults. Newly synthesized proteins were detected by [35S]methionine incorporation. There were only a few differences in the protein profiles of schistosomula from Days 1 to 6 and from adults. Profiles derived from Day 0 schistosomula showed striking differences. Only a few proteins appear to be synthesized on Day 0 under these conditions. Schistosomula on Day 0 synthesized several minor proteins as well as a major protein of approximately 69,000 Da. This protein was immunoprecipitated by rabbit antiserum against bovine uncoating adenosine triphosphatase which recognizes the constitutive and induced 70,000 Da heat shock proteins in a wide variety of eukaryotic cells. More significant differences were observed when the newly synthesized proteins were analyzed by two dimensional gel electrophoresis. The profiles of newly synthesized proteins showed a specific repertoire of expression during the early stages of development in the parasite. A shift in temperature and medium during transformation from aquarium water to isotonic medium may initiate the synthesis of heat shock protein in these parasites.
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PMID:Schistosoma mansoni: protein composition and synthesis during early development; evidence for early synthesis of heat shock proteins. 358 70

Polyadenylated RNA prepared from neonatal rat muscle was translated in a rabbit reticulocyte cell-free system. Two sarcoplasmic reticulum proteins, the Ca2+ + Mg2+-dependent adenosine triphosphatase (ATPase) and calsequestrin, were isolated from the translation mixture by immunoprecipitation, followed by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. The [35S]methionine-labeled translation products were characterized by molecular weight, peptide mapping, and NH2-terminal sequence analysis. The ATPase synthesized in the cell-free system was found to have the same molecular weight (Mr = 100,000) and [35S]-methionine-labeled peptide map as the mature ATPase. The methionine residue present at the NH2 terminus of the mature ATPase was donated by initiator methionyl-tRNArMet and it became acetylated during translation. These results suggest that the ATPase was synthesized without an NH2-terminal signal sequence. Calsequestrin (Mr - 63,000) was synthesized as a higher molecular weight precursor (Mr = 66,000) that contained an additional [35S]methionine-labeled peptide when compared to mature calsequestrin. The NH2-terminal sequence of the precursor was different from the mature protein. The precursor was processed to a polypeptide with a molecular weight identical with mature calsequestrin when microsomal membranes prepared from canine pancreas were included during translation. These results show that calsequestrin is synthesized with an NH2-terminal signal sequence that is removed during translation. These data add to the evidence that the ATPase and calsequestrin follow distinctly different biosynthetic pathways, even though, ultimately, they are both located in the same membrane.
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PMID:Assembly of the sarcoplasmic reticulum. Cell-free synthesis of te Ca2+ + Mg2+-adenosine triphosphatase and calsequestrin. 616 Jan 54


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