Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Phenylglyoxal reacts rapidly with isolated myosin heads (subfragment 1) and induces two successive and distinguishable effects on their enzymic properties: first, a twofold activation of the Ca2+ and Mg2+-dependent ATPases with no effect onthe K+-ATPase followed by inhibition of the K+, Ca2+ and actin-activated Mg2+-ATPases. A specific protein-reagent reagent complex is formed during the second phase of the modification reaction (Ki approximately 5 x 10(-3) M). 2. ADP and ATP with or without cations provide efficient protection only against the loss of ATPase activities, suggesting that the second inhibitory process is occurring at or close to the active site. 3. On the basis of [14C]phenylglyoxal-labelling experiments and the composition of modified subfragment-1 derivatives, it is demonstrated that the sequential modification of two reactive arginyl residues is responsible for the observed activation-inhibition phenomena. Blocking of the first reactive residue produces a shift in the pH/activity curves related to the Ca2+ and Mg2+-dependent ATPases with an apparent activation effect. Modification of the second guanidino group does not destroy the affinity of the protein for the nucleotide substrates but does alter the nucleotide binding site as reflected in the inability of Mg2+. ATP to dissociate the modified subfragment-1--actin complex. It is concluded that electrostatic interactions between this positively charged group and the negatively charged ATP and ADP molecules may be critical for the hydrolytic efficiency of myosin heads. 4. After dissociation and separation of the polypeptide constituents of the protein in acetic acid medium, both labelled sites are found to reside in the heavy chain.
 ...
PMID:Involvement of an arginyl residue in the catalytic activity of myosin heads. 4 10

A purine disulfide analog of ATP, 6,6'-dithiobis(inosinyl imidodiphosphate), forms mixed disulfides with cysteine residues at what are believed to be ATP regulatory sites of myosin. Blocking these sites causes inactivation of the ATPase activity at the active sites. Two cysteine residues per head are specifically modifed by this disulfide analog. The thiopurine nucleotides can be stoichiometrically displaced from myosin by [14-C]cyanide to give a more stable thiocyanato derivative of the enzyme. [14-C]Thiocyanatomyosin (3.7 14-CN/myosin) was dissociated in 4 M urea and the individual subunits were isolated. The heavy chains each had 0.78 14-CN bound per 200,000 molecular weight unit. The light chain with molecular weight of 20,700 had 1.00 14-CN bound and the 16,500 molecular weight light chain had 0.65 14-CN bound. The two 19,000 molecular weight light chains were not labeled. The two labeled light chains have only a single cysteine which is stoichiometrically modified. These two light chains show a high degree of homology and presumably perform identical functions in myosin. Their specific modification by the purine disulfide analog and their other known properties suggest that they contribute directly to the ATP regulatory sites and may, in fact, function as regulatory subunits.
 ...
PMID:Subunit location of sulfhydryl groups of myosin labeled with a purine disulfide analog of adenosine triphosphate. 12 61

The fluorescent reagent, S-mercuric N-dansyl-cysteine, reacts specifically with thiols of the purified Ca2+-ATPase of the sarcoplasmic reticulum, producing an increase of fluorescence of fluorescence intensity at 500 nm (lambda ex = 335 nm). The reaction is stoichiometric, and the increase of the fluorescence intensity is proportional to the number of blocked thiols. Twelve reactive thiols per 10(5) daltons of ATPase peptide fall into roughly three classes. Blocking of the most reactive thiol entails little inhibition of enzyme activity. Blocking of the five thiols reacting next (intermediate class) results in almost complete inhibition of both phosphorylated intermediate formation and ATP hydrolysis. The second order rate constants of the reaction of thiols have been determined by stopped flow studies. The most reactive thiol and the six least reactive thiols can each be treated as a single class with respect to the rate constant; five thiols of intermediate reactivity appear to have different rate constants (k2, k3, ..k6). Of these constants, k1, corresponding to the most reactive thiol, does not change with [Ca2+]. Upon increasing [Ca2+] from 10(-9) to 10(-5) M, k2 increase and k7-12 decreases; the changes roughly parallel the activation of ATPase activity and the Ca2+ binding to the high affinity alpha sites (Ikemoto, N. (1975) J. Biol. Chem. 250, 7219-7224). Upon further increase of [Ca2+] k2 decreases and k7-12 increase, in parallel with the inhibition of ATPase activity and with the Ca2+ binding to the low affinity gamma sites.
 ...
PMID:Ca2+-controlled conformational states of the Ca2+ transport enzyme of sarcoplasmic reticulum. 15 13

The relationship between agonist-sensitive calcium compartments and those discharged by the Ca(2+)-ATPase inhibitor thapsigargin were studied in human platelets. In this context, calcium mobilization from intracellular pools and manganese influx was investigated in relation to the effect of altered cyclic-nucleotide levels. For maximal calcium release from intracellular stores, thapsigargin, compared to a receptor agonist like thrombin, requires the platelet's self-amplification mechanism, known to generate thromboxane A2. With this lipid mediator formed, thapsigargin released calcium and stimulated manganese influx in a manner similar to thrombin. Blocking the thromboxane receptor by addition of sulotroban (BM13.177) or, alternatively, increasing platelet cAMP or cGMP using prostacyclin or sodium nitroprusside, dramatically reduced the ability of thapsigargin to release calcium from intracellular compartments. The same experimental conditions significantly reduced the rate of manganese influx initiated by thapsigargin compared to thrombin. The experiments indicate that thapsigargin-sensitive compartments play only a minor role in inducing manganese influx compared to the receptor-sensitive compartment. Cyclic nucleotides accelerate the redistribution of an agonist-elevated platelet calcium into the thapsigargin-sensitive compartment, from which calcium can be released by inhibition of the Ca(2+)-ATPase. In human platelets, thapsigargin-induced calcium increase and influx were responsible for only part the calcium release resulting from inhibition of the corresponding ATPase; another part results from the indirect effect of thapsigargin acting via thromboxane-A2-receptor activation. Cyclic nucleotides are therefore an interesting regulatory device which can modify the thapsigargin response by not allowing the self-amplification mechanism of platelets to operate.
 ...
PMID:Cyclic nucleotides and intracellular-calcium homeostasis in human platelets. 132 18

Blocking agent of sodium channels in membranes of epithelial cells amiloride and triamterene as well as tetrodotoxin, which blocked sodium channels in electroexcitable membranes, were found to be effective inhibitors of Na, K-ATPase. A similarity between sodium sites of sodium channels and that of Na, K-ATPase is considered.
 ...
PMID:[Inhibition of Na+, K+-ATPase activity by sodium channel blockers]. 241 21

Canine renal Na,K-ATPase was treated with ATP dialdehyde, "oxATP" (20 microM), as described by G. Ponzio, B. Rossi, and M. Lazdunski (1983, J. Biol. Chem. 258, 8201-8205). In this system, a by-product, formaldehyde, was the inactivator. We modified the system to minimize such inhibition and to speed up the reaction. oxATP itself inactivated the enzyme at a rate that was slow at first and later speeded up. We fitted a precursor-product model to the data. Labeling with [3H]oxATP indicated about three sites per alpha beta protomer at complete inactivation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the labeled enzyme showed radioactivity in many components, in the alpha and beta subunits and in small molecules at the tracker dye region. ATP (20 mM) prevented all labeling and inactivation. Ponzio et al. concluded that oxATP labels covalently an ATP binding site. Our experiments did not support this conclusion. Ouabain did not affect labeling. Sodium stimulated both inhibition and labeling more than potassium did, indicating a high-affinity ATP binding site, if any. But nucleotide specificity for preventing or producing inhibition did not correspond to nucleotide specificity for binding of ATP to the native enzyme. Blocking the ATP binding center with fluorescein isothiocyanate or fluorosulfonyl benzoyl adenosine had no effect on [3H]oxATP labeling. ATP also prevented [3H]oxATP labeling of bovine serum albumin or of integral-membrane proteins.
 ...
PMID:Inhibition and labeling of sodium, potassium ATPase by the dialdehyde derivative of ATP. 253 59

The uptake, retention and uptake antagonism of 201Tl-DDC, 201Tl-Cl, 123I-IMP, 99mTc-HMPAO and 99mTc-O4- were compared in rat neocortex cultures. 201Tl-DDC and 123I-IMP revealed the highest uptake of radioactivity in the cultures. 99mTc-HMPAO and 123I-IMP showed the highest retention of radioactivity within the tissue in washout experiments. Blocking of bioelectric activity by tetrodotoxin did not significantly affect the uptake of the radiopharmaceuticals (RPHA). Inhibition of Na-K-ATPase by ouabain inhibited the uptake of 201Tl-Cl (77%) and 201Tl-DDC (27%). Imipramine showed a significantly stronger inhibitory effect on 123I-IMP uptake in comparison with the effect on other RPHA. 99mTc-O4- was not concentrated within the cultured tissue. Under the in vitro conditions used in this study, the various RPHA were characterised by distinct differences in their interaction with cortical brain tissue.
 ...
PMID:Uptake of SPECT radiopharmaceuticals in neocortical brain cultures. 253 15

Subunit specific antiserum can be employed to study the course of ATPase assembly in mitochondria isolated from bakers' yeast. Comparing rates of subunit import with rates of enzyme assembly indicated that no substantial pool of unassembled subunits exists for the three largest ATPase peptides (alpha, beta, and gamma). Blocking import of specific ATPase subunits, however, did reveal a possible accumulation of unassembled alpha and gamma subunits in isolated mitochondria. The kinetic experiments also revealed a lag in the import of beta subunit relative to the uptake of alpha and gamma precursors. Experiments conducted in yeast cells confirmed that beta subunit is assembled soon after it is imported, but did not indicate a delay in import relative to the other subunits of F1.
 ...
PMID:The rate of import and assembly of F1-ATPase in Saccharomyces cerevisiae. 287 70

Previously, we (Suzuki et al. (1978) J. Biochem. 84, 1529) reported that the sedimentation constant of chicken gizzard myosin in the presence of ATP was approximately 10S in 0.15 M or 0.2 M KCl and approximately 6S in 0.3 M or higher concentrations of KCl. The 10S-myosin and 6S-myosin were considerably different in conformation from each other. I now report the finding that the transformation of 6S-myosin to the 10S conformation results in a drastic change in the reactivity of thiol groups of gizzard myosin with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (abbreviated as IAEDANS). The so-called SH1-type thiol groups (Sekine et al. (1962) J. Biol. Chem. 237, 2769) were present on 68 kilodalton fragments (produced by tryptic digestion) of gizzard myosin. The reactivity of the thiol groups with IAEDANS was greatly decreased by the 6S to 10S transformation of gizzard myosin molecules. Two other findings were obtained. Blocking the SH1-type thiol groups made the Mg-ATPase activities (in the presence of gizzard native tropomyosin) of gizzard myosin and of acto-gizzard myosin insensitive to calcium and to phosphorylation of regulatory light chains, although calcium-dependent phosphorylation of the IAEDANS-modified myosin could still occur. It also made gizzard myosin filaments resistant to the disassembly action of ATP.
 ...
PMID:N-Iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine modification of myosin from chicken gizzard. 293 26

Voltage-gated K+ channels are involved in regulation of action potential duration and in setting the resting membrane potential in nerve and muscle. To determine the effects of voltage-gated K+ channel expression on processes not associated with electrically excitable cells, we studied cell volume, membrane potential, Na(+)-K(+)-ATPase activity, and alanine transport after the stable expression of the Kv1.4 and Kv1.5 human K+ channels in Ltk- mouse fibroblasts (L-cells). The fast-activating noninactivating Kv1.5 channel, but not the rapidly inactivating Kv1.4 channel, prevented dexamethasone-induced increases in intracellular volume and inhibited Na(+)-K(+)-ATPase activity by 25%, as measured by 86Rb+ uptake. Alanine transport, measured separately by systems A and ASC, was lower in Kv1.5-expressing cells, indicating that the expression of this channel modified the Na(+)-dependent amino acid transport of both systems. Expression of the Kv1.4 channel did not alter alanine transport relative to wild-type or sham-transfected cells. The changes specific to Kv1.5 expression may be related to the resting membrane potential induced by this channel (-30 mV) in contrast to that measured in wild-type sham-transfected, or Kv1.4-transfected cells (-2 to 0 mV). Blocking of the Kv1.5 channel by 60 microM quinidine negated the effects of Kv1.5 expression on intracellular volume, Na(+)-K(+)-ATPase, and Na(+)-dependent alanine transport. These results indicate that delayed rectifier channels such as Kv1.5 can play a key role in the control of cell membrane potential, cell volume, Na(+)-K(+)-ATPase activity, and electrogenic alanine transport across the plasma membrane of electrically unexcitable cells.
 ...
PMID:Influence of cloned voltage-gated K+ channel expression on alanine transport, Rb+ uptake, and cell volume. 823 76


1 2 3 4 5 6 7 8 Next >>