Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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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)

Amino acid transport rates and amino acid binding proteins were examined in a strain containing the rho-120 mutation (formerly SuA), which has been shown to lower the rho-dependent, ribonucleic acid-activated adenosine triphosphatase activity to 9% of the rho activity in the isogenic wild-type strain. Tryptophan and proline transport, which occur by membrane-bound systems, were not altered. On the other hand, arginine, histidine, leucine, isoleucine, and valine transport were variably increased by a factor of 1.4 to 5.0. Kinetics of leucine transport showed that the LIV (leucine, isoleucine, and valine)-I (binding protein-associated) transport system is increased 8.5-fold, whereas the LIV-II (membrane-bound) system is increased 1.5-fold in the rho mutant under leucine-limited growth conditions. The leucine binding protein is increased fourfold under the same growth conditions. The difference in leucine transport in these strains was greatest during leucine-limited growth; growth on complex media repressed both strains to the same transport activity. We propose that rho-dependent transcriptional termination is important for leucine-specific repression of branched-chain amino acid transport, although rho-independent regulation, presumably by a corepressor-aporepressor-type mechanism, must also occur.
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PMID:Regulation of amino acid transport in Escherichia coli by transcription termination factor rho. 32 70

The uptake of [14C]-histidine and [14C]-histamine and the conversion of [14C]-histidine to [14C]-histamine was measured in suspensions of guinea-pig bone marrow cells rich in basophils. When comparable amounts of labelled histidine or histamine were added to equal numbers of basophils, the uptake of histidine was approximately forty-five times greater than that of histamine. Purified eosinophils, neutrophils and mononuclear cells incorporated only a small proportion of [14C]-histidine when compared to the basophil; [14C]-histamine uptake by all these cell types was virtually negligible. Histidine uptake and the amount of histamine formed de novo was directly related to the number of basophils, the time of incubation and the substrate concentration. Histidine uptake was decreased by agents which inhibit glycolysis, oxidative phosphorylation, Na + - K + -dependent ATPase, protein synthesis and RNA synthesis. Inhibition was demonstrable in a dose-dependent fashion and at concentrations which had no apparent effect on cell viability. Inhibitors of DNA synthesis, and of microtubule function, had no influence on histidine uptake. Cytochalasin B, an inhibitor of microfilament function, also decreased histidine uptake but only at concentrations previously showen to affect hexose transport. None of the agents tested affected the uptake of [14C]-histamine or the amounts of new histamine formed from the histidine that had been incorporated. These studies suggest that histidine is preferentially incorporated into the basophil; that the uptake depends on the integrity of a number of metabolic pathways, but that once the histidine is taken up these requirements do not apply to the formation of new histamine. In contrast, histamine appeared to diffuse passively, and in relatively small amounts, into all the cell types tested.
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PMID:Metabolic studies on the uptake of [14C]-histidine and [14C]-histamine and histamine synthesis by guinea-pig basophils, in vitro. 43 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 effects of 16 group-specific, amino acid-modifying agents were tested on ouabain binding, catalytical activity of membrane-bound (rat brain microsomal), sodium dodecyl sulfate-treated Na+,K(+)-ATPase, and Na+,K(+)-pump activity in intact muscle cells. With few exceptions, the potency of various tryptophan, tyrosine, histidine, amino, and carboxy group-oriented drugs to suppress ouabain binding and Na+,K(+)-ATPase activity correlated with inhibition of the Na+,K(+)-pump electrogenic effect. ATP hydrolysis was more sensitive to inhibition elicited by chemical modification than ouabain binding (membrane-bound or isolated enzyme) and than Na+,K(+)-pump activity. The efficiency of various drugs belonging to the same "specificity" group differed markedly. Tyrosine-oriented tetranitromethane was the only reagent that interfered directly with the cardiac receptor binding site as its inhibition of ouabain binding was completely protected by ouabagenin preincubation. The inhibition elicited by all other reagents was not, or only partially, protected by ouabagenin. It is surprising that agents like diethyl pyrocarbonate (histidine groups) or butanedione (arginine groups), whose action should be oriented to amino acids not involved in the putative ouabain binding site (represented by the -Glu-Tyr-Thr-Trp-Leu-Glu- sequence), are equally effective as agents acting on amino acids present directly in the ouabain binding site. These results support the proposal of long-distance regulation of Na+,K(+)-ATPase active sites.
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PMID:Ouabain binding, ATP hydrolysis, and Na+,K(+)-pump activity during chemical modification of brain and muscle Na+,K(+)-ATPase. 131 Jul 17

The purpose of this study was to explore the role of singlet oxygen in cardiovascular injury. To accomplish this objective, we investigated the effect of singlet oxygen [generated from photoactivation of rose-bengal] on the calcium transport and Ca(2+)-ATPase activity of cardiac sarcoplasmic reticulum and compared these results with those obtained by superoxide radical, hydrogen peroxide and hydroxyl radical. Isolated cardiac SR exposed to rose bengal (10 nM) irradiated at (560 nm) produced a significant inhibition of Ca2+ uptake; from 2.27 +/- 0.05 to 0.62 +/- 0.05 mumol Ca2+/mg.min (mean +/- SE) (P less than 0.01) and Ca(2+)-ATPase activity from 2.08 +/- 0.05 mumol Pi/min.mg to 0.28 +/- 0.04 mumol Pi/min.mg (mean +/- SE) (P less than 0.01). The inhibition of calcium uptake and Ca(2+)-ATPase activity by rose bengal derived activated oxygen (singlet oxygen) was dependent on the duration of exposure and intensity of light. The singlet oxygen scavengers ascorbic acid and histidine significantly protected SR Ca(2+)-ATPase against rose bengal derived activated oxygen species but superoxide dismutase and catalase did not attenuate the inhibition. SDS-polyacrylamide gel electrophoresis of SR exposed to photoactivated rose bengal up to 14 min, demonstrated complete loss of Ca(2+)-ATPase monomer band which was significantly protected by histidine. Irradiation of rose bengal also caused an 18% loss of total sulfhydryl groups of SR. On the other hand, superoxide (generated from xanthine oxidase action on xanthine) and hydroxyl radical (0.5 mM H2O2 + Fe(2+)-EDTA) as well as H2O2 (12 mM) were without any effect on the 97,000 dalton Ca(2+)-ATPase band of sarcoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Singlet oxygen: a potential culprit in myocardial injury? 131 3

The bovine heart mitochondrial F1-ATPase (MF1) is inactivated by 5'-p'-fluorosulfonylbenzoyl-8-azidoadenosine (8-N3-FSBA) with an apparent Kd of 0.47 mM at pH 8.0 and 23 degrees C in the absence of light. Irradiation of dark-inactivated enzyme with long-wavelength UV light produced cross-linked dimers and, to a lesser extent, trimers made up of alpha and beta subunits. Two major radioactive peptides were resolved by high-performance liquid chromatography from tryptic digests of MF1 which had been inactivated with 8-N3-FSB[3H]A at pH 8.0 in the dark. Sequence analysis revealed that one contained Tyr-beta 368 and the other contained His-beta 427 which were labeled in the ratio of 18:15. Sequence analysis of radioactive tryptic peptides isolated from digests of irradiated MF1 derivatized with 8-N3-FSB[3H]A showed that photolysis induced cross-linking of His-427 to Tyr-345 within the same beta subunit in high yield. When MF1 derivatized with 8-N3-FSB[3H]A was irradiated in the presence of beta-mercaptoethanol, alpha-beta cross-links were eliminated, whereas those between His-beta 427 and Tyr-beta 345 were unaffected. Analysis of radioactive peptides in tryptic digests of MF1 derivatized with 8-N3-FSB[3H]A and then irradiated in the presence or absence of beta-mercaptoethanol showed that the nitrene generated from reagent attached to Tyr-beta 368 participates in formation of alpha-beta cross-links in the absence of beta-mercaptoethanol. Therefore, the nitrene generated from reagent tethered to His-beta 427 is shielded from solvent and reacts with the side chain of Tyr-beta 345. In contrast, the nitrene generated from reagent attached to Tyr-beta 368 is exposed to solvent, but in the absence of scavengers reacts with side chains present in the alpha subunit. Irradiation of MF1, partially inactivated with 8-N3-FSBA, led to loss of residual ATPase activity without affecting residual ITPase activity. The amount of photoinactivation was greater when partial dark inactivation was performed at pH 6.9, where modification of His-beta 427 predominates, than when performed at pH 8.0, where modification of Tyr-beta 368 predominates. This suggests that cross-linking of His-beta 427 to Tyr-beta 345, and not cross-linking of alpha and beta subunits, is responsible for the augmented inactivation induced by irradiation.
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PMID:Irradiation of the bovine mitochondrial F1-ATPase previously inactivated with 5'-p-fluorosulfonylbenzoyl-8-azido-[3H]adenosine cross-links His-beta 427 to Tyr-beta 345 within the same beta subunit. 132 8

We investigated the susceptibility of sarcolemmal Na+K(+)-ATPase to singlet oxygen. The role of this enzyme is regulation of Na+ concentration and thereby membrane potential. Inhibition of Na+ pump would lead to intracellular Ca2+ overload therefore further aggravating the injury caused by free radicals. Incubation of isolated sarcolemmal vesicles with irradiated rose bengal (150 nM) resulted in 86 +/- 1% inhibition of Na+K(+)-ATPase activity and histidine (25-100 mM) protected the enzyme in a dose-dependent fashion whereas SOD, catalase or mannitol (.OH radical scavenger) did not have any effect. Also, the inhibition of Na+K(+)-ATPase activity was dependent on rose bengal concentration, intensity of irradiation, duration of light exposure, showing that inhibition was directly related to amount of singlet oxygen generated. These results show that singlet oxygen may have significant disruptive effects on sarcolemmal function and may represent an important mechanism by which the oxidative injury to the myocardium induces arrhythmogenesis.
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PMID:Singlet oxygen-induced inhibition of cardiac sarcolemmal Na+K(+)-ATPase. 132 12

Coumarins are inhibitors of the ATP hydrolysis and DNA supercoiling reactions catalysed by DNA gyrase. Their target is the B subunit of gyrase (GyrB), encoded by the gyrB gene. The exact mode and site of action of the drugs is unknown. We have identified four mutations conferring coumarin resistance to Escherichia coli: Arg-136 to Cys, His or Ser and Gly-164 to Val. In vitro, the ATPase and supercoiling activities of the mutant GyrB proteins are reduced relative to the wild-type enzyme and show resistance to the coumarin antibiotics. Significant differences in the susceptibility of mutant GyrB proteins to inhibition by either chlorobiocin and novobiocin or coumermycin have been found, suggesting wider contacts between coumermycin and GyrB. We discuss the significance of Arg-136 and Gly-164 in relation to the notion that coumarin drugs act as competitive inhibitors of the ATPase reaction.
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PMID:gyrB mutations which confer coumarin resistance also affect DNA supercoiling and ATP hydrolysis by Escherichia coli DNA gyrase. 132 22

The Monarch (Danaus plexippus) sequesters cardiac glycosides for its chemical defence against predators. Larvae and adults of this butterfly are insensitive towards dietary cardiac glycosides, whereas other Lepidoptera, such as Manduca sexta and Creatonotos transiens are sensitive and intoxicated by ouabain. Ouabain inhibits the Na+,K(+)-ATPase by binding to its alpha-subunit. We have amplified and cloned the DNA sequence encoding the respective ouabain binding site. Instead of the amino acid asparagine at position 122 in ouabain-sensitive insects, the Monarch has a histidine in the putative ouabain binding site, which consists of about 12 amino acids. This change may explain the ouabain insensitivity.
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PMID:Molecular basis for the insensitivity of the Monarch (Danaus plexippus) to cardiac glycosides. 133 51


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