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

---

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

The maltose transport system of Escherichia coli is a well-characterized member of the ATP binding cassette transporter superfamily. Members of this family share sequence similarity surrounding two short sequences (the Walker A and B sequences) which constitute a nucleotide binding pocket. It is likely that the energy from binding and hydrolysis of ATP is used to accomplish the translocation of substrate from one location to another. Periplasmic binding protein-dependent transport systems, like the maltose transport system of E.coli, possess a water-soluble ligand binding protein that is essential for transport activity. In addition to delivering ligand to the membrane-bound components of the system on the external face of the membrane, the interaction of the binding protein with the membrane complex initiates a signal that is transmitted to the ATP binding subunit on the cytosolic side and stimulates its hydrolytic activity. Mutations that alter the membrane complex so that it transports independently of the periplasmic binding protein also result in constitutive activation of the ATPase. Genetic analysis indicates that, in general, two mutations are required for binding protein-independent transport and constitutive ATPase. The mutations alter residues that cluster to specific regions within the membrane spanning segments of the integral membrane components MalF and MalG. Individually, the mutations perturb the ability of MBP to interact productively with the membrane complex. Genetic alteration of this signalling pathway suggests that other agents might have similar effects. These could be potentially useful for modulating the activities of ABC transporters such as P-glycoprotein or CFTR, that are implicated in disease.
...
PMID:Mutations that alter the transmembrane signalling pathway in an ATP binding cassette (ABC) transporter. 815 12

A 160-kDa plasma membrane protein of the yeast Saccharomyces cerevisiae was overexpressed by mutating the PDR1 or the PDR3 transcription factor gene. The protein is the membrane-bound ATP binding cassette transporter PDR5 (Balzi, E., Wang, M., Leterme, S., Van Dyck, L., and Goffeau, A. (1994) J. Biol. Chem. 269, 2206-2214). PDR5 was solubilized with n-dodecyl-beta-D-malto-side and separated from the PMA1 plasma membrane H(+)-ATPase by glycerol gradient centrifugation. The PDR5 protein hydrolyzes nucleoside diphosphates and triphosphates. This activity is sensitive to low concentrations of vanadate, of oligomycin, and of a variety of hydrophobic compounds. Many of these properties liken PDR5 to the purified mammalian P-glycoprotein responsible for multidrug resistance.
...
PMID:Solubilization and characterization of the overexpressed PDR5 multidrug resistance nucleotide triphosphatase of yeast. 817 92

Daunomycin, an anti-neoplastic agent, is known to be sequestered by acidic organelles in normal and multidrug-resistant cells [Willingham, M.C., Cornwell, M.M., Cardarelli, C.O., Gottesman, M.M., & Pastan, I. (1986) Cancer Res. 46, 5941-5946]. We studied the mechanism of accumulation of daunomycin into acidic organelles using chromaffin granule vesicles and proteoliposomes reconstituted with purified F-type H(+)-ATPase as model systems. Radiolabeled daunomycin was taken up by chromaffin vesicles upon addition of ATP. Its ATP-dependent uptake was stimulated about 1.4- to 1.8-fold by valinomycin plus K+, but was inhibited by ammonium chloride (10 mM) and nigericin plus K+. Quinidine (5 microM), verapamil (5 microM), or vanadate (0.5 mM), inhibitors of P-glycoprotein, had no effect on its uptake. Daunomycin was also taken up by liposomes reconstituted with F-type H(+)-ATPase. Furthermore, doxorubicin and vinblastine were taken up by these vesicles, whereas colchicine and rhodamine 123 were not. The accumulations of daunomycin and doxorubicin in acidic organelles of cultured cells were decreased by inhibiting vacuolar ATPase by addition of bafilomycin A1 or concanamycin A, or by increasing the internal pH by addition of nigericin. Melittin and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide dissipated the delta pH and inhibited accumulation of daunomycin in the membrane vesicles and acidic organelles in cultured cells. These results indicate that the delta pH established by vacuolar-type ATPase drives the uptake of daunomycin, doxorubicin or vinblastine into acidic organelles, and that no specific transporters are involved in their uptakes.
...
PMID:ATP-dependent uptake of anti-neoplastic agents by acidic organelles. 820 70

The plasmid-determined arsenite and antimonite efflux ATPase of bacteria differs from other membrane transport ATPases, which are classified into several families (such as the F0F1-type H(+)-translocating ATP synthases, the related vacuolar H(+)-translocating ATPases, the P-type cation-translocating ATPases, and the superfamily which includes the periplasmic binding-protein-dependent systems in Gram-negative bacteria, the human multidrug resistance P-glycoprotein, and the cystic fibrosis transport regulator). The amino acid sequences of the components of the arsenic resistance system are not similar to known ATPase proteins. New findings with the arsenic resistance operons of bacterial plasmids suggest that instead of being an orphan the Ars system will now be the first recognized member of a new class of ATPases. Furthermore, fundamental questions of energy-coupling (ATP-driven or chemiosmotic) have recently been raised and the finding that the arsC gene product is a soluble enzyme that reduces arsenate to arsenite changes the previous picture of the functioning of this widespread bacterial system.
...
PMID:Orphan enzyme or patriarch of a new tribe: the arsenic resistance ATPase of bacterial plasmids. 833 56

The haemolysin exporter HlyB and its homologues are central to the unconventional signal-peptide-independent secretion of toxins, proteases and nodulation proteins by bacteria. HlyB is a member of the ATP-binding cassette (ABC) or traffic ATPase superfamily, and resembles closely in structure and function mammalian exporters such as the multidrug-resistance P-glycoprotein, combining both integral membrane and cytosolic domains. Overproduction of the HlyB cytoplasmic domain as a C-terminal peptide fused to glutathione S-transferase allowed the direct affinity purification and concentration of 30-50 mg ml-1 of soluble protein (GST-Bctp) in an apparently dimeric form possessing both transferase and ATPase activity. GST-Bctp bound to ADP-agarose and was eluted specifically by ATP and ADP, affinity behaviour which was confirmed in both the full-length HlyB and the unfused HlyB cytoplasmic domain synthesized in vitro. The stoichiometry of binding to MgATP and MgADP was close to equimolar and both ligands induced substantial conformational change in the protein. Mg(2+)-dependent ATPase activity of GST-Bctp (Vmax 1 mumol min-1 mg-1, Km 0.2 mM) was comparable with the activity of the bacterial importer MalK and human P-glycoprotein reconstituted into proteoliposomes, and over an order of magnitude higher than in vitro measurements of disaggregated MalK purified from inclusion bodies. Activity was unaffected by inhibitors of F- and V-type ATPases, non-hydrolysable ATP analogues, or translocation substrate, but was severely inhibited by inhibitors of E1E2 (P-type) ATPases, and the acidic phospholipid phosphatidyl glycerol.
...
PMID:ATPase activity and ATP/ADP-induced conformational change in the soluble domain of the bacterial protein translocator HlyB. 836 61

Binding protein-dependent transport systems mediate the accumulation of several ions, sugars, amino acids, and peptides in Gram-negative bacteria by using the energy of ATP hydrolysis and belong to a superfamily of membrane proteins which extends to eukaryotic cells and includes the multidrug resistance P-glycoprotein and the cystic fibrosis transmembrane conductance regulator. The binding protein-dependent galactose transport system of Salmonella typhimurium comprises four proteins which have been characterized previously by molecular cloning experiments (51,000-dalton MglA protein, with a stable proteolytic product of 38,000 daltons, 33,000-dalton MglB protein, 29,000-dalton MglC protein, 21,000-dalton MglE protein). By using a MglA hyperproducing strain, we have purified a galactose-stimulated ATPase which shows a single band in polyacrylamide gels under nondenaturing conditions and shows three bands at 51,000, 38,000, and 15,000 daltons on sodium dodecyl sulfate-polyacrylamide gels (our results suggest that the bands at 38,000 and 15,000 daltons represent proteolytic products of the 51,000-dalton protein). The ATPase activity coincides with the purified protein during the two last chromatographic steps of the purification procedure, and it cannot be isolated from a strain which does not contain the mglA gene. The MglA ATPase is stimulated 3-fold by galactose and hydrolyzes ATP to ADP and Pi (Km ATP = 60 microM, Ka galactose = 0.3 mM, Vmax = 140 nmol/min/mg of protein). The gamma-phosphate of ATP is transferred neither to galactose nor to the protein itself. Vanadate, N-ethylmaleimide and 5-methoxyindole-2-carboxylic acid, a specific inhibitor of binding protein-dependent transport systems, inhibit the MglA ATPase.
...
PMID:The MglA component of the binding protein-dependent galactose transport system of Salmonella typhimurium is a galactose-stimulated ATPase. 838 96

The characteristics of P-glycoprotein (MDR1), an ATP-dependent drug extrusion pump responsible for the multidrug resistance of human cancer, were investigated in an in vitro expression system. The wild-type and several mutants of the human MDR1 cDNA were engineered into recombinant baculoviruses and the mutant proteins were expressed in Sf9 insect cells. In isolated cell membrane preparations of the virus-infected cells the MDR1-dependent drug-stimulated ATPase activity, and 8-azido-ATP binding to the MDR1 protein were studied. We found that when lysines 433 and/or 1076 were replaced by methionines in the ATP-binding domains, all these mutations abolished drug-stimulated ATPase activity independent of the MgATP concentrations applied. Photoaffinity labeling with 8-azido-ATP showed that the double lysine mutant had a decreased ATP-binding affinity. In the MDR1 mutant containing a Gly185 to Val replacement we found no significant alteration in the maximum activity of the MDR1-ATPase or in its activation by verapamil and vinblastine, and this mutation did not modify the MgATP affinity or the 8-azido-ATP binding of the transporter either. However, the Gly185 to Val mutation significantly increased the stimulation of the MDR1-ATPase by colchicine and etoposide, while slightly decreasing its stimulation by vincristine. These shifts closely correspond to the effects of this mutation on the drug-resistance profile, as observed in tumor cells. These data indicate that the Sf9-baculovirus expression system for MDR1 provides an efficient tool for examining structure-function relationships and molecular characteristics of this clinically important enzyme.
...
PMID:Altered drug-stimulated ATPase activity in mutants of the human multidrug resistance protein. 856 33

Multidrug resistance (MDR) to chemically unrelated therapeutic anticancer agents in mammalian cells is mediated by the overexpression of an ATP-dependent 150- to 180-kD membrane glycoprotein P-glycoprotein (P-gp). Although the complete physiological role of P-gp is unknown, it is proposed to function in cellular detoxification of xenobiotics. In this study, we investigated whether the organophosphorus insecticide chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridinyl phosphorothioate) or its metabolites interact with P-gp. Immunohistochemical analysis of tissues from male Fischer 344 rats administered chlorpyrifos (7.6 mg/kg gavage) showed increased P-gp expression in the kidney, adrenal, liver, jejunum, and stomach (tissues associated with elimination of xenobiotics), compared to control tissues. The most prominent increase was detected in the large bile ducts of the liver and the proximal tubule region of the kidney. P-gp expression was increased throughout the adrenal medulla and cortex, while a moderate increase was detected in the epithelial layers of the stomach and jejunum. To examine further the interaction between chlorpyrifos and P-gp, we evaluated whether chlorpyrifos or its active metabolite, chlorpyrifos oxon, could inhibit [3H]azidopine labeling of P-gp in MDR1 baculovirus-infected insect Sf9 cells. A concentration-dependent inhibition of [3H]azidopine labeling of P-gp was detected with chlorpyrifos oxon, while significant inhibition was not detected with chlorpyrifos. To correlate the binding of chlorpyrifos oxon to P-gp with a biochemical effect, we examined its ability to stimulate P-gp-mediated ATPase activity in these Sf9 cells. Chlorpyrifos oxon stimulated P-gp ATPase activity 1.75 times that of the positive control (10 microM verapamil). Taken together, these results suggest that chlorpyrifos oxon interacts with P-gp, and support the hypothesis that P-gp may play a role in the cellular detoxification of insecticides in mammalian tissues. To our knowledge this is the first report of an organophosphorus insecticide interacting with and increasing the expression of P-gp.
...
PMID:Chlorpyrifos oxon interacts with the mammalian multidrug resistance protein, P-glycoprotein. 860 Feb 91

The aim of the present study was to demonstrate that the modulation of P-glycoprotein (Pgp) ATPase activity by peptides, drugs, and chemosensitizers takes place on a common drug pharmacophore. To this end, a highly emetine-resistant Chinese hamster ovary cell line was established, in which Pgp constituted 18% of plasma membrane protein. Reconstituted proteoliposomes, the Pgp content of which was up to 40%, displayed a basal activity of 2.6 +/- 0.45 micromol of Pi/min/mg of protein, suggesting the presence of an endogenous Pgp substrate. This basal ATPase activity was stimulated (up to 5.2 micromol of Pi/min/mg of protein) by valinomycin and various Pgp substrates, whereas, to our surprise, gramicidin D, an established Pgp substrate, was inhibitory. Taking advantage of this novel inhibition of Pgp ATPase activity by gramicidin D, a drug competition assay was devised in which gramicidin D-inhibited Pgp ATPase was coincubated with increasing concentrations of various substrates that stimulate its ATPase activity. Gramicidin D inhibition of Pgp ATPase was reversed by Pgp substrates, including various cytotoxic agents and chemosensitizers. The inhibition of the basal ATPase activity and the reversal of gramicidin D inhibition of Pgp ATPase by its various substrates conformed to classical Michaelis-Menten competition. This competition involved an endogenous substrate, the inhibitory drug gramicidin D, and a stimulatory substrate. We conclude that the various MDR type substrates and chemosensitizers compete on a common drug binding site present in Pgp.
...
PMID:Competition of hydrophobic peptides, cytotoxic drugs, and chemosensitizers on a common P-glycoprotein pharmacophore as revealed by its ATPase activity. 862 16

We have recently described an ATP-driven, valinomycin-dependent 86Rb+uptake into proteoliposomes reconstituted with mammalian P-glycoprotein (Eytan, G. D., Borgnia, M. J., Regev, R., and Assaraf, Y. G. (1994) J. Biol. Chem. 269, 26058-26065). P-glycoprotein mediated the ATP-dependent uptake of 86Rb+-ionophore complex into the proteoliposomes, where the radioactive cation was accumulated, thus, circumventing the obstacle posed by the hydrophobicity of P-glycoprotein substrates in transport studies. Taking advantage of this assay and of the high levels of P-glycoprotein expression in multidrug-resistant Chinese hamster ovary cells, we measured simultaneously both the ATPase and transport activities of P-glycoprotein under identical conditions and observed 0.5-0.8 ionophore molecules transported/ATP molecule hydrolyzed. The amount of 86Rb+ ions transported within 1 min via the ATP- and valinomycin-dependent P-glycoprotein was equivalent to an intravesicular cation concentration of 8 mM. Thus, this stoichiometry and transport capacity of P-glycoprotein resemble various ion-translocating ATPases, that handle millimolar substrate concentrations. This constitutes the first demonstration of comparable rates of P-glycoprotein-catalyzed substrate transport and ATP hydrolysis.
...
PMID:Functional reconstitution of P-glycoprotein reveals an apparent near stoichiometric drug transport to ATP hydrolysis. 862 17


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---