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)

Previous studies have indicated that rat luteal cells at certain stages of development can be fractionated so as to obtain two plasma membrane fractions with different densities and different profiles of marker enzymes. The light membrane fractions (density 1.13) contain the majority of hCG-binding sites and little or no cyclase enzyme, while the heavy membranes (density 1.17) contain the majority of cyclase enzyme and lesser quantities of hormone-binding sites. These membrane fractions were further compared with respect to their susceptibility to perturbation by digitonin. The buoyant density of luteal cell light membrane fractions, as marked by [125I]iodo-hCG binding, Mg2+-dependent ATPase, and 5'-nucleotidase, were highly perturbable by digotonin (delta density, greater than 0.05), while adenylate cyclase activity and phosphodiesterase activity associated with this fraction were only slightly perturbed (delta density, less than 0.02). The buoyant density of luteal cell heavy membrane fractions, as marked by adenylate cyclase, ATPase, and nucleotidase, was not significantly perturbed by digotonin. The hCG binding associated with the heavy membrane fraction was not perturbed by digitonin. From these studies, we conclude that the adenylate cyclase activity associated with light membrane fractions is due to contamination by heavy membranes, while the hCG-binding activity in heavy membrane fractions is intrinsic to that membrane. Except for the lysosomal marker (glucuronidase), which was solubilized by digitonin, the detergent had no significant effect on the density of mitochondrial, Golgi, GERL (Golgi, endoplasmic reticulum, and lysomal), or endoplasmic reticulum membranes. Plasma membranes from isolated granulosa cells and ovaries obtained 24 h after priming with PMS gonadotropin-hCG behaved as heavy membranes (density, 1.17) which contained hCG-binding sites, adenylate cyclase, nucleotidase, and Mg2+-dependent ATPase. These were not significantly perturbed by digitonin. The appearance of light membranes and the segregation of adenylate cyclase from the majority of hCG-binding sites is a development feature of the luteal cell.
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PMID:Interactions of gonadotropins with corpus luteum surface membranes. V. Differential effects of digitonin on the buoyant densities of light and heavy rat ovarian membrane fractions. 43 71

An Escherichia coli mutant pleiotropically altered in membrane-bound oxidoreductase activities was isolated following nitrosoguanidine treatment. Mutant R23 was able to grow on glucose, but was unable to grow on succinate or other oxidizable substrates as a sole energy source. Isolated membranes prepared from R23 failed to oxidize succinate and formate; while NADH was oxidized at a reduced rate by membranes. The mutant also exhibited markedly reduced cytochrome content, but normal DL-lactate PMS reductase and H(+)-translocating ATPase activities relative to the parent strain. Bacteriophage Plkc was used to transduce R23 to growth on glycerol, DL-lactate or succinate; regardless of the selection procedure, each of the 179 transductants had gained the ability to grow on all three substrates. The suc- mutation in R23 appeared to be responsible for the loss of growth on oxidizable substrates, altered membrane-bound oxidoreductase activities, resistance to neomycin, and reduced levels of cytochrome components. The suc- mutation was localized in the 6 to 6.5 min region of the E. coli chromosome map utilizing episomal transfers.
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PMID:Characterization of an Escherichia coli mutant pleiotropically altered in membrane-bound oxidoreductase activities. 214 97

Treatment of chloroplasts with trypsin activates a light-requiring ATPase whose properties are strikingly similar to those of the light-requiring ADP kinase of chloroplasts. The observations here presented suggest that there exists, in chloroplasts, a reducible enzyme which, in its reduced state, catalyzes the reversible reaction: P(i) (-2) + ADP(-3) + H(+) right harpoon over left harpoon ATP(-4) + H(2)O. By reduction and protonation of the catalytic site of this enzyme, light-driven electron flow in the chloroplast drives the reaction to the right. Hydrolysis of ATP proceeds only when the enzyme is reduced and when the proton concentration within the chloroplast is kept at low levels, viz., in the absence of light, in the presence of uncoupling agents which decrease the concentration of internal H(+), or in the presence of electron acceptors which by oxidizing the internal electron acceptors also decrease the proton potential. Activation of the enzyme requires light; it remains active only in the presence of ATP. Hydrolysis of all the ATP results in inactivation of the ATPase. The membrane-bound protein CF(2) limits the reversibility of the reaction by excluding ATP and H(2)O from the enzyme site. It also facilitates the ability of the chloroplasts to accumulate and to maintain high internal concentrations of such ions as ADP, P(i), PMS(+), and imidazole.
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PMID:ADP kinase and ATPase in chloroplasts. 424 Jun 84

Recently proposed mechanisms of site II energy transduction that assign a key role to cytochrome b-566 are based on the finding that the apparent midpoint potential of b-566 in animal mitochondria increases by more than 250 mV upon addition of ATP [Chance et al. (1970) Proc. Nat. Acad. Sci. USA 66, 1175-1182]. However, since it has never been shown that the redox mediators used in the midpoint potential measurements equilibrate directly with b-566, the observed midpoint potential shift could merely reflect reversed electron transport. In mung bean mitochondria, the apparent midpoint potential of b-566 is known to be unaffected by addition of ATP [Dutton and Storey (1971) Plant Physiol. 47, 282-288]. In the present work, mung bean b-566 is shown to undergo an ATP-induced reduction similar to that observed for b-566 in animal mitochondria. However, in mung bean mitochondria the reduction is found to be rapidly relaxed by addition of redox mediator (phenazine methosulfate, PMS) and concomitantly PMS causes a marked, antimycinsensitive stimulation of ATPase activity. These results suggest that the ATP-induced reduction in mung bean mitochondria is due to reversed electron transport and that PMS can effectively short-circuit reversed electron transport in this system, bringing it close to equilibrium. Moreover, since mung bean and animal b-566 are identical in all other respects tested, the results support the idea that the apparent midpoint potential shift in animal mitochondria is also merely due to reversed electron transport, and that the mediators are now not effective enough to bring the system to equilibrium.
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PMID:On the lack of ATP-induced midpoint potential shift for cytochrome b-566 in plant mitochondria. 427 93

The gamma-subunit of chloroplast coupling factor 1 contains a disulfide bond which is involved in the redox regulation of the enzyme. In all the sequence plant gamma-subunits this disulfide bond is separated by a five amino acid spacer region. To investigate the regulatory significance of this region genetic transformation experiments were performed with Chlamydomonas reinhardtii. C. reinhardtii strain atpC1 (nitl-305, cw 15, mt-), which does not accumulate the CF1 gamma-subunit polypeptide, was independently transformed with two constructs, each bearing mutations within the disulfide bond spacer region between Cys198 and Cys204 of the gamma-subunit. Successful complementation was confirmed by phenotypic selection, Northern blot analysis, and reverse transcription polymerase chain reaction. Whereas wild-type thylakoid membrane particles catalyze in vitro, PMS-dependent photophosphorylation that is stimulated 2-fold by the addition of DTT, similar particles from each of the mutant strains exhibit rates of ATP synthesis that are independent of DTT. Consistent with these results, wild-type CF1 ATPase activity is stimulated by DTT which is in contrast to the ATPase activities of both the mutant strains which are independent of DTT addition. These results suggest a role of the gamma-subunit disulfide bond spacer region in the redox regulation of chloroplast ATP synthase.
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PMID:A role for the disulfide bond spacer region of the Chlamydomonas reinhardtii coupling factor 1 gamma-subunit in redox regulation of ATP synthase. 878 38