Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: HUMANGGP:009336 (ATPase)
 59,826 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purple membrane of Halobacterium halobium acts as a light-driven proton pump, ejecting protons from the cell interior into the medium and generating electrochemical proton gradient across the cell membrane. However, the type response of cells to light as measured with a pH electrode in the medium consists of an initial net inflow of protons which subsides and is then replaced by a net outflow which exponentially approaches a new lower steady state pH level. When the light turned off a small transient acidification occurs before the pH returns to the original dark level. We present experiments suggesting that the initial inflow of protons is triggered by the beginning ejection of protons through the purple membrane and that the initial inflow rate is larger than the continuing light-driven outflow. When the initial inflow has decreased exponentially to a small value, the outflow dominates and causes the net acidification of the medium. The initial inflow is apparently driven by a pre-existing electrochemical gradient across the membrane, which the cells can maintain for extended times in the absence of light and oxygen. Treatments which collapse this gradient such as addition of small concentrations of uncouplers abolish the initial inflow. The triggered inflow occurs through the ATPase and is accompanied by ATP synthesis. Inhibitors of the ATPase such as N,N'-dicyclohexylcarbodiimide (DCCD) inhibit ATP synthesis and abolish the inflow. They also abolish the transient light-off acidification, which is apparently caused by a short burst of ATP hydrolysis before the enzyme is blocked by its endogenous inhibitor. Similar transient inflows and outflows of protons are also observed when anaerobic cells are exposed to short oxygen pulses.
 ...
PMID:Light-driven proton translocations in Halobacterium halobium. 0 22

Stable membrane proteins and lipids are convenient to study biomembranes. Two stable proton translocating proteins were purified and reconstituted into vesicles capable of proton translocation. One was a thermostable ATPase (TF0-F1) of thermophilic bacterium PS3 and the other was rhodopsin of Halobacterium halobium. TF0-F1 was composed of a proton pump moiety (TF1) and a proton channel moiety (TF0). TF1 was the first membrane ATPase which was crystallized and reconstituted from its five polypeptides. Like TF0 and TF1, the rhodopsin in purple membrane was highly stable against dissociating agents, acids and alkali. Phospholipids of these biomembranes were also stable and contained no unsaturated fatty acyl groups. The molecular species of the phospholipids of PS3 were determined by mass chromatography. Measurements were made of the difference in electrochemical potential of protons (deltamicronH+) across the membrane of the reconstituted vesicles. The deltamicronH+ attained was 312 mV in TF0-F1 vesciles and was 230 mV in the rhodopsin vesicles. To conclude that electron transport components are not necessary for ATP synthesis in energy yielding biomembranes, two experiments were performed: The ATP synthesis was observed i) on acid-base treatment of TF0-F1 vesicles, and ii) on illumination of the rhodopsin-TF0-F1 vesicles.
 ...
PMID:Proton translocation by ATPase and bacteriorhodopsin. 1 75

Acetyl phosphatidylethanolamine was compared with phosphatidylethanolamine in the reconstitution of several biological membrane activities with the following results. 1. The proton pump reconstituted with the purple membrane of Halobacterium halobium and acetyl phosphatidylethanolamine was quite active. However, some differences in the kinetic properties, particularly in the decay rate, were noted between vesicles reconsituted with phosphatidylethanolamine and acetyl phosphatidylethanolamine. 2. Acetyl phosphatidylethanolamine could not replace phosphatidylethanolamine in the reconstitution of a Ca-2 plus pump with ATPase isolated from sacoplasmic reticulum. However, inclusion of suitable amounts of stearylamine or oleylamine during reconstitution yielded acetyl phosphatidylethanolamine vesicles with Ca-2 plus translocation activity comparable to that of phosphatidylethanolamine vesicles. 3. A mixture of acetyl phosphatidylethanolamine and stearylamine or oleylamine substituted for phosphatidylethanolamine in the reconstitution of mitochondrial hydrophobic proteins to form vesicles that catalyze 32-Pi-ATP exchange. Since phosphatidylcholine is also required in this system, these findings point to two functions of phosphatidylethanolamine, one related to the specific properties of its amino group, the other to a structural role of its small polar head group. A hydrophobic alkylamine can fullfill the first function, acetyl phosphatidylethanolamine the second. 4. The importance of the charge was also observed in experiments with the reconstituted rutamycin-sensitive ATPase of mitochondria. After depletion of phospholipids from the hydrophobic proteins, ATPase activity and rutamycin sensitivity were restored only if a phospholipid as well as the appropriate charge were present.
 ...
PMID:Acetyl phosphatidylethanolamine in the reconstitution of ion pumps. 12 78

1. Oxidative phosphorylation was reconstituted with a mitochondrial proton pump (oligomycin-sensitive ATPase) and segments of the oxidation chain (cytochrome oxidase or DPNH-Q1 reductase). A proton pump of bacteriorhodopsin substituted for the respiratory chain components, giving rise to light-induced ATP formation. 2. Since oxidative phosphorylation has thus become a special case of the problem of ion translocation in general, we have investigated and reconsituted other pumps. The reconstituted Ca++ pump of sarcoplasmic reticulum consists of two factors, the Ca++-dependent ATPase and a heat-stable coupling factor. 3. Other information obtained from reconstitution experiments include the role of asymmetry in organized membranes and the specificity of protein-phospholipid interaction. 4. Purified preparations of Ca++-ATPase catalyze the formation of ATP from Pi and ADP in a stepwise reaction stoichiometric with the enzyme and dependent on Ca++.
 ...
PMID:Resolution and reconstitution of ion-transport systems. 13 Aug 18

At very low concentrations (less than 1 muM) triphenyltin chloride inhibits ATP formation and coupled electron transport in isolated spinach chloroplasts. Basal (-Pi) and uncoupled electron transport are not affected by triphenyltin. The membrane-bount ATP in equilibrium Pi exchange and Mg2+-dependent ATPase activities of chloroplasts are also completely sensitive to triphenyltin, although the Ca2+-dependent and Mg2+-dependent ATPase activities of the isolated coupling factor protein are insensitive to triphenyltin. The light-driven proton pump in chloroplasts is stimulated (up to 60%) by low levels of triphenyltin. Indeed, the amount of triphenyltin necessary to inhibit ATP formation or stimulate proton uptake is dependent upon the amount of chloroplasts present in the reaction mixture, with an apparent stoichiometry of 2-2.5 triphenyltin molecules/100 chlorophyll molecules at 50% inhibition of ATP formation and half-maximal stimulation of proton uptake. Chloroplasts partially stripped of coupling factor by an EDTA was are no longer able to accumulate protons in the light. However, low levels of triphenyltin can effectively restore this ability. The amount of triphenyltin required for the restoration of net proton uptake is also dependent upon the amount of chloroplasts, with a stoichiometry of 4-5 triphenyltin molecules/100 chlorophyll molecules at 50% reconstitution. On the basis of this and other evidence it is concluded that triphenyltin chloride inhibits phosphorylation, ATP + Pi exchange and membrane-bound ATPase activities in chloroplasts by specifically blocking the transport of protons through a membrane-bound carrier or channel located in a hydrophobic region of the membrane at or near the functional binding site for the coupling factor.
 ...
PMID:Inhibition by triphenyltin chloride of a tightly-bound membrane component involved in photophosphorylation. 13 Oct 35

Electrophilic agents--derivatives of carbonic acids--are found to inhibit respiration, ATP synthesis and reverse electrone transport in intact mitochondria. The inhibition of respiration and ATPase was observed in intact mitochondria at 3 and 3u states (by Chance). Inhibitors concentrations, which caused 50% inhibition, were approximately the same. Sharp decrease of the effect of electrophilic inhibitors on respiration and ATPase activity in mitochondria and submitochondrial particles with substantially impaired coupling system was observed. The following conclusions are drawn on the basis of the data obtained: 1) electrophilic inhibitor attack the coupling site of respiration and ATP synthesis in mitochondria; 2) the reaction of the proton transport from the respiration proton pump to ATP synthetase is one of the slowest steps of the process of ATP-synthesis in mitochondria. A scheme of working the coupling system is suggested which includes the step of proton lateral diffusion.
 ...
PMID:[Inhibitors of the slow stage of proton transfer in the link connecting respiration with mitochondrial phosphorylation]. 13 96

The plasma membrane of Saccharomyces cerevisiae has a Mg2+-dependent ATPase which is distinct from the mitochondrial Mg2+-ATPase and at the pH optimum of 5.5 has a Km for ATP of 1.7 mM and a Vmax of 0.42 mumol of ATP hydrolyzed/mg/min. At least three protein components of the crude membrane (Mr = 210,000, 160,000 and 115,000) are labeled with [gamma"32P]ATP at pH 5.5. These phosphoproteins form rapidly in the presence of Mg2+, rapidly turn over the bound phosphate when unlabeled ATP is added, and dephosphorylate after incubation in the presence of hydroxylamine. Vanadate, an inhibitor of the Mg2+-ATPase activity, blocks the phosphorylation of the 210,000- and 115,000-dalton proteins. At pH 7.0, only the 210,000- and 160,000-dalton proteins are phosphorylated. While these three phosphorylated intermediates have not been unambiguously identified as components of the Mg2+-ATPase, the finding of such phosphorylated components in association with that activity implies that this enzyme differs in mechanism from the mitochondrial proton pump and that it is similar in mechanism to the metal ion pumps ((Na+-K+)-ATPase and Ca2+-ATPase) of the mammalian plasma membrane.
 ...
PMID:Characterization of the plasma membrane Mg2+-ATPase from the yeast, Saccharomyces cerevisiae. 15 66

We have studied the composition of ATP-driven proton pumps from bovine heart mitochondria and have reconstituted the oligomycin-sensitive ATPase complex from its individual components. The complex contains 9 to 10 subunits of which 5 are assembled in the soluble F1 protein, 2 are required for the attachment of F1 to the membrane and 2 form the proton channel within the membrane. With the help of information obtained from studies of the chloroplast and the bacterial proton pumps, we can tentatively assign a function to each of the subunits of the pump. The position of F1 outside of the membrane seen in electron micrographs of negatively stained preparations, does not appear to be an artifact. Evidence from immunological studies, chemical derivatizations as well as further electron microscopy (positive staining and freeze-etching), support this statement. We describe in this paper a 28 000-dalton polypeptide which has been isolated from the mitochondria membrane and is required for the reconstitution of oligomycin-sensitive ATPase and 32Pi-ATP exchange activity. We propose a mechanism of action of the proton pump in which the key energy-yielding reaction is the binding of Mg2+ to the protein. The function of the proton gradient is to displace Mg2+ from this site to permit cyclic repetition of the binding process. Essential for this scheme is the cyclic opening and closing of the proton channel. We have outlined our present approaches to test this hypothesis.
 ...
PMID:Components and mechanism of action of ATP-driven proton pumps. 23 97

Aqueous suspensions of bacteriorhodopsin in purple membrane fragments from Halobacterium halobium have bben subjected to microsecond flash photometry utilizing both unpolarized and polarized light. Depletion of the ground state chromophore centered at 570 nm is accompanied by the formation of transients absorbing maximally at 410 nm and 660 nm with rise times of about 0.4 and 6 ms, respectively. Decay of both transients and reformation of the ground state chromophore occurs with identical first-order kinetics with a half life of about 6 ms. All three chromophores are polarized with dichroic ratios which remain constant throughout the transient lifetimes, indicating that Brownian rotation of the chromophore within the membrane is considerably restricted. Whereas agents which induce permeability of membranes to protons (2,4-dinitrophenol, carbonylcyanide-m-chlorophenylhydrazone) and non-specific univalent cations (gramicidin) or inhibit ATPase (ouabain) had no influence, the K+-specific ionophore valinomycin in the presence of K+ inhibited and quenched the formation of the 660 nm transient with concomitant increase in lifetime of the 410 nm transient and delay in recovery of the 570 nm chromophore. High concentrations of Na+ produced an effect similar to that of valinomycin. The relationship of these data to the mechanism of the proton pump in the intact bacterium is discussed, with the conclusion that the 410 nm transient performs a key role.
 ...
PMID:Kinetic studies of phototransients in bacteriorhodopsin. 124 9

Gastric (H+/K+)-ATPase, the proton pump of the parietal cell, is responsible for the final step of acid secretion in the stomach. In 1981, picoprazole, a substituted benzimidazole, was found to inhibit (H+/K+)-ATPase. It was reported in 1983 that omeprazole has the most potent efficacy among the substituted benzimidazoles and today, omeprazole has been used for treatment of gastroduodenal disease. Recently, lansoprazole, similar to omeprazole in chemical structure, was developed in Japan, and several other compounds, such as pantoprazole, E-3810 and NC-1300-O-3, have also been reported to suppress acid secretion through inhibition of (H+/K+)-ATPase. In the present paper the background of the discovery of (H+/K+)-ATPase and development of proton pump inhibitors is reviewed.
 ...
PMID:[Discovery and development of the proton pump inhibitor]. 131 79


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