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)

Stimulation of gastric acid secretion is mediated by cAMP which regulates the proton pump through an A-kinase-dependent phosphoprotein. The purpose of this study was to isolate a stimulation-dependent gastric phosphoprotein capable of stimulating acid secretion. Gastric glands were prepared from rabbit gastric mucosa and acid secretion was stimulated with cAMP. A detergent extract of these stimulated gastric membranes was fractionated by gel chromatography and assayed for functional activity by measurement of [14C]-aminopyrine accumulation in permeabilized resting gastric glands or measurement of H(+)-K(+)-ATPase activity in inhibited gastric microsomes. We hereby report isolation of a membrane-bound, A-kinase-dependent phosphoprotein which enhances aminopyrine accumulation in digitonin-permeabilized gastric glands (32%) and stimulates H(+)-K(+)-ATPase activity in gastric microsomes to a level 55% of the maximal stimulation observed in the presence of valinomycin. Incubation of this phosphoprotein with [32P]ATP and the catalytic subunit of A-kinase resulted in [32P] incorporation into a protein which coincided with a single protein band on SDS-PAGE (17,500 Da).
...
PMID:Isolation of a gastric phosphoprotein which stimulates acid secretion. 132 65

Soluble thiamine triphosphatase (EC 3.6.1.28) of bovine brain has been purified 68,000-fold to an electrophoretically homogeneous state with an overall recovery of 5.5% by hydrophobic chromatography on Toyopearl HW-60, Sephadex G-75 gel filtration, DEAE-Toyopearl 650M chromatography and Blue Sepharose CL-4B chromatography. The enzyme has an absolute specificity among thiamine and nucleoside phosphate esters for thiamine triphosphate and shows no nonspecific phosphatase activities. Thiamine triphosphatase is composed of a single polypeptide chain with molecular mass of 33,900 kDa as estimated by Sephadex G-100 gel filtration and SDS-polyacrylamide gel electrophoresis. The enzyme has a pH optimum of 8.7 and is dependent on divalent metal ions. Mg2+ has been found to be the most effective among cations tested. A study of the reaction kinetics over a wide range of thiamine triphosphate concentrations has revealed a biphasic saturation curve being described by higher-degree rational polynomials.
...
PMID:Purification and characterization of thiamine triphosphatase from bovine brain. 132 71

A (Ca(2+)-Mg2+)-ATPase associated with rat liver lysosomal membranes was purified about 300-fold over the lysosomal membranes with a 7% recovery as determined from the pattern on polyacrylamide gel electrophoresis in the presence of SDS. The purification procedure included: preparation of lysosomal membranes, solubilization of the membrane with Triton X-100, WGA-Sepharose 6B, Con A-Sepharose, hydroxylapatite chromatography, and preparative polyacrylamide gel electrophoresis. The molecular mass, estimated by gel filtration with Sephacryl S-300 HR, was approximately 340 kDa, and SDS-polyacrylamide gel electrophoresis showed the enzyme to be composed of four identical subunits with an apparent molecular mass of 85 kDa. The isoelectric point of the purified enzyme was 3.6. The enzyme had a pH optimum of 4.5, a Km value for ATP of 0.17 mM and a Vmax of 71.4 mumol/min/mg protein at 37 degrees C. This enzyme hydrolyzed nucleotide triphosphates and ADP but did not act on p-nitrophenyl phosphate and AMP. The effects of Ca2+ and Mg2+ on the ATPase were not additive, thereby indicating that both Ca2+ and Mg(2+)-ATPase activities are manifested by the same enzyme. The (Ca(2+)-Mg2+)-ATPase differed from H(+)-ATPase in lysosomal membranes, since the enzyme was not inhibited by N-ethylmaleimide but was inhibited by vanadate. The effects of some other metal ions and compounds on this enzyme were also investigated. The N-terminal 18 residues of (Ca(2+)-Mg2+)-ATPase were determined.
...
PMID:Purification and characterization of (Ca2+-Mg2+)-ATPase in rat liver lysosomal membranes. 133 Oct 35

Human DNA helicase III, a novel DNA unwinding enzyme, has been purified to apparent homogeneity from nuclear extracts of HeLa cells and characterized. The activity was measured by using a strand displacement assay with a 32P labeled oligonucleotide annealed to M13 ssDNA. From 305 grams of cultured cells 0.26 mg of pure protein was isolated which was free of DNA topoisomerase, ligase, nicking and nuclease activities. The apparent molecular weight is 46 kDa on SDS polyacrylamide gel electrophoresis. The enzyme shows also DNA dependent ATPase activity and moves unidirectionally along the bound strand in 3' to 5' direction. It prefers ATP to dATP as a cofactor and requires a divalent cation (Mg2+ > Mn2+). Helicase III cannot unwind either blunt-ended duplex DNA or DNA-RNA hybrids and requires more than 84 bases of ssDNA in order to exert its unwinding activity. This enzyme is unique among human helicases as it requires a fork-like structure on the substrate for maximum activity, contrary to the previously described human DNA helicases I and IV, (Tuteja et al. Nucleic Acids Res. 18, 6785-6792, 1990; Tuteja et al. Nucleic Acids Res. 19, 3613-3618, 1991).
...
PMID:DNA helicase III from HeLa cells: an enzyme that acts preferentially on partially unwound DNA duplexes. 133 86

Na,K-ATPase was purified from pig and mink kidney. Enzyme batches of high specific activity apparently contained only alpha- and beta-peptides, judging from the SDS-gel-electrophoretic pattern. Careful determinations of the ouabain-binding capacity and binding kinetics were carried out. The question whether the functional unit is an alpha beta-protomer, a diprotomer or even a polymer was analysed from the binding stoichiometry and the binding pattern at nonsaturating ouabain concentrations. The binding capacity exceeded half of the theoretical maximum value for exclusively alpha beta-promoters. A half-of-the-sites reactivity of a diprotomer thus seems less likely, though nearly half of the protein is not accounted for in its absence. When ouabain binding took place in the presence of Na+, at least two binding components were noticed. Most probably the two components are not of equal size, thus excluding a co-operative diprotomer construction of the active ouabain-binding units. If the co-operativity model has to be abandoned, the phenomenon could be due to two or more isozymes exhibiting different Na(+)-affinities. Isoforms of the hydrolytic alpha-peptide were analysed by an ELISA technique and on blots of Na,K-ATPase peptides utilizing commercial isoform-specific antibodies. Though not absolutely specific, the individual antibodies were assumed to be monospecific with respect to the single isoforms of the alpha-peptide. In that case, data were consistent with a significant contribution of alpha 2- and alpha 3-isoforms (about 15%), in addition to the predominant alpha 1-isoform in kidney Na,K-ATPase.
...
PMID:Heterogeneity of Na,K-ATPase from kidney. 133 54

The sarcoplasmic Ca(2+)-ATPase was reduced with 300 mM 2-mercaptoethanol at elevated temperatures (40-45 degrees C) with a concomitant loss of ATPase activity. The reduction and inactivation of the Ca(2+)-ATPase proceeded rapidly in the absence of Ca2+. The Ca(2+)-ATPase was also inactivated with 2-mercaptoethanol in the presence of diluted SDS (0.4 mg/ml) even at 20 degrees C. In contrast to the (Na+, K+) ATPase, the inactivated Ca(2+)-ATPase in the presence of diluted SDS was sedimented by the centrifugation at 100,000 x g for 30 min.
...
PMID:Reduction and inactivation of the sarcoplasmic Ca(2+)-ATPase by 2-mercaptoethanol--contrast to the (Na+,K+) ATPase. 133 62

Many neurohormones alter the force of cardiac contraction by variations in the intracellular Ca2+ concentration. alpha 1-Adrenergic and muscarinic stimulations, rather, modify the sensitivity of contractile proteins to Ca(2+)-calmodulin-myosin light-chain kinase (MLCK) complex induces a large increase in Ca2+ sensitivity (0.14 pCa unit) of these easily accessible myofilaments. This increase is further enhanced by up to 0.19 pCa unit when protein kinase C (PKC) is added together with MLCK. Similarly, the Ca2+ ATPase activity of skinned cells in suspension is increased in the presence of MLCK and further in the presence of both kinases. 32P-labelling and SDS/PAGE show that these changes are associated with light-chain 2 (LC2) phosphorylation together with phosphorylation of troponin I and troponin T when PKC is added. Although to a smaller extent than in smooth muscle, phosphorylation of cardiac myosin LC2 may be involved in the modulation of heart contractility.
...
PMID:Protein kinase C enhances myosin light-chain kinase effects on force development and ATPase activity in rat single skinned cardiac cells. 138 18

The expression of troponin T, a thin filament regulatory protein, was examined in normal and failing left ventricles. The samples were obtained from the hearts of patients with severe heart failure who were undergoing cardiac transplantation, and from normal adult hearts that could not be used for transplantation. Western blots of the myofibrillar proteins demonstrated two isoforms, troponin T 1 (TnT1) and troponin T 2 (TnT2). TnT2 is expressed at significantly higher levels in failing hearts (p less than 0.004). Western blots of two-dimension SDS-PAGE gels resolved two dominant spots of TnT1 and of TnT2 and several minor troponin T species. Alkaline phosphatase treatment markedly decreased the sizes of the two acidic spots while increasing the two more basic spots by a comparable amount. Myofibrillar ATPase activity had an inverse and negative linear relationship (r = 0.7, p less than 0.02) with the myofibrillar percentage of total troponin T comprised of TnT2. In that heart failure in these transplant patients had multiple bases, we propose that rather than a cause of heart failure, the disease-associated changes in troponin T isoform expression are an adaptation to abnormal myocardial function.
...
PMID:Troponin T isoform expression in the normal and failing human left ventricle: a correlation with myofibrillar ATPase activity. 138 29

Fluorescein 5'-isothiocyanate (FITC) was used to modify the lysine residue in the active site of tonoplast H(+)-ATPase from etiolated mung-bean (Vigna radiata L.) seedlings. FITC caused marked inactivation of the enzyme activities of both membrane-bound and soluble ATPase and its associated H+ translocation. The SDS/PAGE pattern revealed that the FITC-binding site was in the large (A) subunit of ATPase. Inhibition could be substantially prevented by its physiological substrate ATP, pyrophosphate and nucleotides in the decreasing order: ATP greater than pyrophosphate greater than ADP greater than AMP greater than GTP greater than CTP greater than UTP. The mode of inhibition by FITC was competitive with respect to ATP. Loss of ATPase activity followed pseudo-first-order kinetics with a Ki of 0.33 mM, a minimum inactivation half-time of 110 s, and a first-order rate constant of 0.244 s-1. A double-logarithmic plot of apparent rate constant versus FITC concentration gave a slope of 0.913, indicating that inactivation results from reaction of at least one lysine residue at the catalytic site of the large subunit. Labelling studies indicated that the incorporation of approx. 1 mol of FITC/mol of ATPase is sufficient to inhibit ATPase completely. The enhancement and blue shift of emission maxima of FITC after modification of ATPase indicated that the labelled lysine residue was located in a relatively hydrophobic domain.
...
PMID:Inhibition of tonoplast ATPase from etiolated mung bean seedlings by fluorescein 5'-isothiocyanate. 138 33

We have analyzed extragenic suppressors of paralyzed flagella mutations in Chlamydomonas reinhardtii in an effort to identify new dynein mutations. A temperature-sensitive allele of the PF16 locus was mutagenized and then screened for revertants that could swim at the restrictive temperature (Dutcher et al. 1984. J. Cell Biol. 98:229-236). In backcrosses of one of the revertant strains to wild-type, we recovered both the original pf16 mutation and a second, unlinked suppressor mutation with its own flagellar phenotype. This mutation has been identified by both recombination and complementation tests as a new allele of the previously uncharacterized PF9 locus on linkage group XII/XIII. SDS-PAGE analysis of isolated flagellar axonemes and dynein extracts has demonstrated that the pf9 strains are missing four polypeptides that form the I1 inner arm dynein subunit. The primary effect of the loss of the I1 subunit is a decrease in the forward swimming velocity due to a change in the flagellar waveform. Both the flagellar beat frequency and the axonemal ATPase activity are nearly wild-type. Examination of axonemes by thin section electron microscopy and image averaging methods reveals that a specific domain of the inner arm complex is missing in the pf9 mutant strains (see accompanying paper by Mastronarde et al.). When combined with other flagellar defects, the loss of the I1 subunit has synergistic effects on both flagellar assembly and flagellar motility. These synthetic phenotypes provide a screen for new suppressor mutations in other loci. Using this approach, we have identified the first interactive suppressors of a dynein arm mutation and an unusual bypass suppressor mutation.
...
PMID:Extragenic suppressors of paralyzed flagellar mutations in Chlamydomonas reinhardtii identify loci that alter the inner dynein arms. 138 4


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

---