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PubMed1972

Activation of the adenosine triphosphatase of Limulus polyphemus actomyosin by tropomyosin.

Purified actin does not stimulate the adenosine triphosphatase (ATPase) activity of Limulus myosin greatly. The ATPase activity of such reconstituted preparations is only about one-fourth the ATPase of myofibrils or of natural actomyosin. Actin preparations containing tropomyosin, however, activate Limulus myosin fully. Both the tropomyosin and the actin preparations appear to be pure when tested by different techniques. Tropomyosin combines with actin but not with myosin and full activation is reached at a tropomyosin-to-actin ratio likely to be present in muscle. Tropomyosin and actin of several different animals stimulate the ATPase of Limulus myosin. Tropomyosin, however, is not required for the ATPases of scallop and rabbit myosin which are fully activated by pure actin alone. Evidence is presented that Limulus myosin, in the presence of ATP at low ionic strength, has a higher affinity for actin modified by tropomyosin than for pure actin.

Actins↗
PubMed1975

Role of phospholipid in the intermediate steps of the sodium-plus-potassium ion-dependent adenosine triphosphatase reaction.

The phosphorylation and dephosphorylation steps of the (Na-++K-+)-dependent ATPase (adenosine triphosphatase) (EC 3.6.1.3) reaction have been compared in 'normal', lipid-depleted and 'restored' membrane ATPase preparations. Partial lipid depletion was achieved by a single extraction with Lubrol W, and 'restoration' by adding pure phosphatidylserine. Gamma-32-P-labelled ATP was used for phosphorylation. The main findings were as follows. (1) Partial lipid depletion decreased but did not prevent Na-+-dependent phosphorylation, although it virtually abolished both Na-+-dependent and (Na-++K-+)-dependent ATPase activities. (2) 'Restoration' with phosphatidylserine produced an increment in phosphorylation that was the same in the presence and absence of added Na-+. (3) K-+ decreased the extent of Na-+-dependent phosphorylation of the depleted enzyme without producing a corresponding release of Pi. (4) K-+ rapidly decreased the extent of phosphorylation of the 'restored' enzyme to near-background value, with a concomitant release of Pi. (5) Na-+-dependent ATP hydrolysis was not restored. (6) The turnover of the 'restored' enzyme seemed to be higher than that of the 'normal' enzyme. The reaction sequence is discussed in relation to these results and the fact that the depleted enzyme retained about 50% of K-+-dependent phosphatase activity.

Adenosine Triphosphatases↗
PubMed1978

Mitochondrial adenosine triphosphatase of wild-type and poky Neurospora crassa.

We have compared the adenosine triphosphatase (ATPase) activity of mitochondria prepared from wild-type Neurospora crassa and from poky, a maternally inherited mutant known to possess defective mitochondrial ribosomes and reduced amounts of cytochromes aa3 and b. poky contains two distinct forms of mitochondrial ATPase. The first is normal in its Km for ATP, specificity for nucleotides and divalent cations, pH optimum, cold stability, and sensitivity to inhibitors (oligomycin, N,N-dicyclohexyl carbodiimide, and adenylyl imidodiphosphate). The fact that membrane-bound, cold-stable, oligomycin-sensitive ATPase activity is present in poky (with an activity of 1.93 +/- 0.03 mumol/min-mg of protein compared with 1.33 +/- 0.07 mumol/min-mg of protein in the wild-type strain) and also in chloramphenicol-grown wild-type cells suggests that products of mitochondrial protein synthesis play only a limited role in the attachment of the mitochondrial ATPase to the membrane in Neurospora. poky also contains a second form of mitochondrial ATPase, which has an activity of 1.5 +/- 0.2 mumol/min-mg of protein, is oligomycin sensitive but cold labile, and presumably is attached less firmly to the mitochondrial membrane. The two forms, added together, represent a substantial overproduction of mitochondrial ATPase by poky.

Adenosine Triphosphatases↗
PubMed1975

Na+-K+-activated adenosine triphosphatase and intestinal electrolyte transport. Effect of adrenal steroids.

Sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) is associated with electrolyte transport in many tissues. To help delineate its role in intestinal transport, changes in rat intestinal electrolyte and water transport induced by injecting methylprednisolone acetate 3 mg/100 g or deoxycorticosterone acetate (DOCA) 0.5 mg/100 g per day for 3 days were correlated with changes in Na-K-ATPase activity. Methylprednisolone increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the jejunum, ileum, and colon. Examination of isolated epithelial cells demonstrated that the jejunal and ileal increase in Na-K-ATPase occurred in both the villus tip and crypermeability, Mg-ATPase, and adenylate cyclase activities were unchanged by methylprednisolone. DOCA increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the colon alone. Colonic Mg-ATPase and adenylate cyclase activities were unaffected. Jejunal and ileal enzyme activity, electrolyte transport, and permeability were unchanged by DOCA. Methylprednisolone and DOCA were not additive in their effect on colonic Na-K-ATPase activity. Methylprednisolone and DOCA increased electrolyte and water transport and Na-K-ATPase activity concomitantly in specific segments of small intestine and colon. These data are consistent with an important role for Na-K-ATPase in intestinal electrolyte and water transport.

Adenosine Triphosphatases↗
PubMed1981

The presence of two hydrolytic sites on beef heart mitochondrial adenosine triphosphatase.

The ribose-modified nucleotides 2',3'-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP) and TNP-ADP were used to probe the catalytic sites on soluble beef heart mitochondrial adenosine triphosphatase (F1). Both compounds were potent competitive inhibitors of ATP hydrolysis catalyzed by F1, Ki = 5.5 and 10 nM, respectively, and by submitochondrial particles, Ki (TNP-ATP) = 21 nM. Both compounds also were potent competitive inhibitors of ATP synthesis during oxidative phosphorylation (Ki = 1300 nM). Both analogs inhibited the 32Pi-ATP exchange reaction and the ATP-dependent reduction of NAD+ by succinate, catalyzed by submitochondrial particles. TNP-ATP and TNP-ADP were bound by F1. The presence of two binding sites on the enzyme for TNP-adenine nucleotides was determined by titrations of difference absorbance spectra, of the increase in fluorescence of the analog which occurred upon interaction with protein, and by titrations with the centrifuge column method using 32P-labeled TNP-adenine nucleotides. The first binding site bound the analogs with an affinity too high to be measured. The Kd for analog binding by the second site was 20 to 80 nM. In the presence of Mg2+, the 2 sites were filled with the TNP-ATP at a rate too rapid to be resolved by the procedure used. TNP-[gamma-32P]ATP was hydrolyzed by F1, Km = 0.2 microM, Vmax = 1.1 mol of 32Pi formed/mol of F1/s. It was shown, using the isotope trap technique as well as the inhibitor efrapeptin, that the 2 binding sites for TNP-ATP on F1 are hydrolytic sites.

Adenine Nucleotides↗
PubMed1979

Re-evaluation of the relationship between the positive inotropic effect of ouabain and its inhibitory effect on (Na+ + K+)-dependent adenosine triphosphatase in rabbit and dog hearts.

Previous studies have shown that in the ouabain-exposed rabbit heart, although positive inotropy and inhibition of (Na+ + K+)-dependent adenosine triphosphatase are induced concomitantly, the extent of inhibition of the enzyme remains constant when positive inotropy is washed out; and in the dog heart, if positive inotropy without arrhythmias is induced by ouabain, inhibition of the enzyme is not detected. The purpose of this work was the re-evaluation of these previous findings. Rapid recovery of the enzyme from small tissue samples was achieved by homogenization in 1 M KCl and centrifugation. When the enzyme was prepared by this method from ouabain-exposed rabbit and dog hearts, ouabain remained bound to the enzyme. The extent of inhibition of the enzyme was measured by the fluorimetric assay of K+-dependent 3-O-methylfluorescein phosphatase before and after removal of bound ouabain. Correlation between the extent of inhibition of this activity and that of (Na+ + K+)-dependent adenosine triphosphatase activity was established. Utilizing these refined methods, the following results were obtained. In the rabbit heart, positive inotropy and enzyme inhibition occurred concomitantly. Washout of the effect resulted in partial reactivation of the enzyme. In the dog heart, the previous findings were confirmed. The results are not inconsistent with the hypothesis that enzyme inhibition is the cause of the positive inotropic effects. They do suggest, however, the need for further testing of the hypothesis.

Animals↗
PubMed1981

Three genes coding for subunits of the membrane sector (F0) of the Escherichia coli adenosine triphosphatase complex.

Two mutant unc alleles, unc-469 and unc-476, have been characterized as affecting a previously undescribed gene, designated uncF. The uncF gene is part of the unc operon (with the gene order being uncBFEAGDC), although some uncertainty remains as to the relative order of the uncF and uncE genes. Mutant strains carrying the uncF469 or uncF476 allele lack the 18,000-molecular-weight component of the F0 sector of the adenosine triphosphatase in the cell membrane but retain the dicyclohexylcarbodiimide-binding protein (molecular weight, 8,400). Conversely, strains carrying mutations in the uncE gene lack the dicyclohexylcarbodiimide-binding protein but retain the 18,000-molecular-weight protein in the cell membrane. Strains carrying mutations in the uncB gene have both the 18,000-molecular-weight protein and the dicyclohexylcarbodiimide-binding protein present in the cell membranes. The three proteins of the F0 portion of the adenosine triphosphatase, viz., 24,000, 18,000, and 8,400 molecular weights, became membrane associated after in vitro transcription-translation with plasmid pAN51 as template. Plasmids carrying deletions which affected the UncBFE region were isolated from plasmid pAN51 and characterized genetically. A comparison of the genes that were absent from the various deletion plasmids with the membrane-associated products formed after in vitro transcription-translation indicated that the uncB gene coded for the 24,000-molecular-weight protein and that the gene order was probably uncBFE. A correlation between length of deoxyribonucleic acid, genes present, and their products is presented in relation to plasmid pAN51.

Adenosine Triphosphatases↗
PubMed1978

The functional unit of calcium-plus-magnesium-ion-dependent adenosine triphosphatase from sarcoplasmic reticulum. The aggregational state of the deoxycholate-solubilized protein in an enzymically active form.

Vesicles consisting of (Ca(2+)+Mg(2+))-dependent ATPase (adenosine triphosphatase), and lipid were prepared from sarcoplasmic reticulum of rabbit skeletal muscle. As with non-ionic detergents [le Maire, Møller & Tanford (1976) Biochemistry15, 2336-2342] the (Ca(2+)+Mg(2+))-dependent ATPase after solubilization by deoxycholate showed a pronounced tendency to form oligomers in gel-chromatographic experiments, when eluted in the presence of deoxycholate and phosphatidylcholine. To evaluate the functional significance of oligomer formation the properties of enzymically active preparations of ATPase, solubilized by deoxycholate, were studied. Such preparations were obtained at a protein concentration of 2.5mg/ml in the presence of a high salt concentration (0.4m-KCl) and sucrose (0.3m) in the solubilization medium. Analytical ultracentrifugation of solubilized ATPase showed one protein boundary moving at the same rate as gel-chromatographically prepared monomeric ATPase (s(20,w)=6.0S). From simultaneous measurements of the diffusion coefficient an apparent molecular weight of 133000 was calculated, consistent with solubilization of ATPase in predominantly monomeric form. The enzymic activity of deoxycholate-solubilized ATPase when measured directly in the solubilization medium at optimal Ca(2+) and MgATP concentrations was about 35-50% of that of vesicular ATPase. The dependence of enzymic activity on MgATP concentration indicated that the solubilized ATPase retained high-affinity binding of MgATP, but the presence of high concentrations of the nucleotide did not stimulate activity further, in contrast with that of vesicular ATPase. The dependence of enzymic activity on the free Ca(2+) concentration was essentially the same for both solubilized and vesicular forms, indicating that interaction of ATPase with more than one molecule of Ca(2+) is required for enzyme activity. Solubilized enzyme at 20 degrees C was phosphorylated to about the same degree as vesicular ATPase. It is concluded that the catalytic activity of monomeric ATPase retains most of the features of vesicular ATPase and that extensive oligomer formation in gel-chromatographic experiments in the presence of deoxycholate probably reflects processes taking place during inactivation and delipidation of the protein.

Adenosine Triphosphatases↗
PubMed1987

Ouabain binding to brain (Na+,K+)-adenosine triphosphatase: interactions of K+, ethanol and norepinephrine with high- and low-affinity binding.

Effects of K+, ethanol and norepinephrine on the binding kinetics of ouabain to (Na+,K+)-adenosine triphosphatase in beef brain microsomes were examined. K+ reduced the rate and apparent affinity for ouabain binding markedly. Whereas ethanol and norepinephrine themselves inhibited ouabain binding slightly, they stimulated binding in the presence of K+. Norepinephrine enhanced the effect of ethanol. Dissociation of ouabain was biphasic, with fast and slow components corresponding to high and low apparent affinity. About 65% of the enzyme had high affinity, regardless of conditions. Norepinephrine and ethanol had differential effects on the rate of dissociation from high and low affinity enzyme, however. Alpha receptor blockade generally prevented the effects of norepinephrine. These results show that, although norepinephrine and ethanol have a modest effect on the amount of enzyme that can bind ouabain, their main effect on (Na+,K+)-adenosine triphosphatase is to antagonize the binding of K+ to its allosteric site that inhibits ouabain binding. The data support the hypothesis that ouabain binds rapidly to a K+-insensitive form of phosphorylenzyme or to its dephosphorylated analog and dissociates rapidly from E1.

Animals↗
PubMed1977

Phosphorylation from adenosine triphosphate of sodium- and potassium-activated adenosine triphosphatase. Comparison of enzyme-ligand complexes as precursors to the phosphoenzyme.

The relative effectiveness of the ligands Mg2+, Na+, and ATP in preparing sodium plus potassium ion transport adenosine triphosphatase for phosphorylation was studied by means of a rapid mixing apparatus. Addition of 2 mM MgC12, 120 mM NaC1, and 5 muM [gamma-32P]ATP simultaneously to the free enzyme gave an initial phosphorylation rate of about 0.3 mu mol-mg-1-min-1 at 25 degrees and pH7.4. Addition of Mg2+ to the enzyme beforehand, separately or in combination with Na+ or ATP, had little effect on the initial rate. Addition of Na+ only to the enzyme beforehand increased this rate 1.5- to 3-fold. Early addition of ATP 130 ms before Na+ plus Mg2+ increased the rate 6- to 7-fold. Early addition of Na+ plus ATP was most effective; it increased the rate about 10-fold. The data indicate that Na+ and ATP bind in a random order and that each ligand potentiates the effect of the other. The rate of dissociation of ATP from the enzyme was estimated by a chase of unlabeled ATP of variable duration. This rate was slowest in the presence of Mg2+ (k = 540 min-1), most rapid in the presence of Na+ (k = 2000 min-1), and intermediate (k = 1100 min-1) in the absence of metal ions. The effect of Na+ concentration on the rate of phosphorylation was estimated when Na+ with Mg2+ was added to the enzyme-ATP complex. The rate followed Michaelis-Menten kinetics with a maximum of 2.9 mu mol-mg-1 and a Km of 8 mM. The effect of Na+ concentration was also estimated on the increment in the rate of phosphorylation produced by the presence of Na+ with the enzyme-ATP complex beforehand. The increment followed the same kinetics with a maximum of 3.75 mu mol-mg-1-min-1 and a Km of 5.4 mM. In both cases estimation of the Hill coefficient failed to show cooperativity between binding sites for Na+. In contrast, the dependence of ouabain-sensitive ATPase activity on Na+ concentration in the absence of K+ indicated two sites for Na+ with apparent Km values of 0.16 and 8.1 mM, respectively.

Adenosine Triphosphatases↗
PubMed1985

Transmural distribution of isomyosin in rabbit ventricle during maturation examined by immunofluorescence and staining for calcium-activated adenosine triphosphatase.

Mammalian ventricle contains two major isomyosins, V1 and V3, which differ in the primary structure of their heavy chains (HC alpha alpha and HC beta beta, respectively) and in their adenosine triphosphatase activity. The distribution of the HC alpha isomyosin in the left ventricle of the rabbit was followed as a function of age and transmural location. HC alpha was detected with a monoclonal antibody found to be specific for the hinge region of V1 myosin molecules when viewed in the electron microscope after low-angle rotary shadowing. Frozen sections were observed with indirect immunofluorescence developed to this anti-HC alpha hinge antibody. Serial sections were observed with the histochemical assay for calcium-activated myosin adenosine triphosphatase, using preincubation at various pH levels. Results show that all the ventricular myocytes in baby rabbits (2 weeks) are stained by the HC alpha-antibody from the epi- to endocardium. The isomyosin content of myocytes varies through the epi- to endocardium of the right ventricular wall of the adult (1-year-old) rabbit, with the HC alpha form predominating in the outer epicardial third of the wall and the lowest amount of HC alpha in the middle third of the wall. A mixture of stained and unstained myocytes is seen in the endo- and subendocardial regions. The spatial distribution of HC alpha in 4-month-old rabbits varies between that of the baby and adult. There is good agreement between myocyte classifications made by histochemical and antibody staining methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1976

Molecular weights and hydrophobicity of the polypeptide chain of sarcoplasmic reticulum calcium(II) adenosine triphosphatase and of its primary tryptic fragments.

The polypeptide chain of the Ca2+-stimulated adenosine triphosphatase from sarcoplasmic reticulum has a molecular weight of 119 000+/-6500 on the basis of sedimentation equilibrium measurements in sodium dodecyl sulfate. The two primary fragments obtained by limited proteolysis each have within experimental error the same molecular weight, corresponding to one-half the molecular weight of the whole chain. Both fragments are eqaully resistant to complete denaturation by guanidine hydrochloride, a property characteristic of many intrinsic membrane proteins. This suggests that the native enzyme has two membrane-embedded halves, with an externally accessible link between them.

Adenosine Triphosphatases↗
PubMed1973

Regulation by membrane fluidity of the allosteric behavior of the (Ca2)-adenosine triphosphatase from Escherichia coli.

The allosteric properties of the membrane-bound (Ca(2+))-adenosine triphosphatase of an unsaturated fatty acid auxotroph of Escherichia coli were studied in membranes with different fatty acid compositions. The Hill coefficient of the inhibition by Na(+) ranged from 1.4, in the case where the auxotroph was grown with cis-vaccenic acid as supplement, to 2.8 when grown on linolenic acid. The results indicate that no fatty acid is particularly involved in the allosteric phenomena. A correlation between the values of the Hill coefficient and the double bond index or the ratio of the double bond index saturated to the fatty acids of the membrane was found. These facts are interpreted as a modulation by the membrane fluidity of the allosteric behavior of the membrane-bound enzyme. The general biological character of this phenomenon is discussed in this paper.

Adenosine Triphosphatases↗
PubMed2001

Sepsis increases the plasma membrane content of alpha1 and alpha2 isoforms of Na+-K+ adenosine triphosphatase in rat skeletal muscle.

HYPOTHESIS: Increased Na(+)-K(+) adenosine triphosphatase (ATPase) activity in skeletal muscle during sepsis is caused by transient increases in enzyme content within the plasma membrane. DESIGN: Randomized controlled study. SETTING: University laboratory. INTERVENTION: Eighty-eight adult male Wistar rats were randomly assigned to undergo cecal ligation and puncture (CLP) or sham operation. MAIN OUTCOME MEASURES: Gastrocnemius muscles were harvested 6, 12, 24, and 48 hours after operation and Na(+)-K(+) ATPase activities were measured spectrofluorimetrically. Messenger RNA (mRNA) levels for the alpha1 and alpha2 isoforms of Na(+)-K(+) ATPase were determined by Northern blot analysis. Crude membranes, internal membranes, and purified plasma membranes were isolated from gastrocnemius muscles and protein levels of alpha1 and alpha2 isoforms were determined by Western blot analysis. RESULTS: Na(+)-K(+) ATPase activity in the CLP group was significantly higher compared with the sham group 24 hours after operation (P<.05). However, there were no differences between the sham and CLP groups 6, 12, or 48 hours after operation. No significant differences between the CLP and sham groups were noted in mRNA levels for Na(+)-K(+) ATPase alpha1 and alpha2 isoforms. Western blot analysis revealed that the plasma membrane (but not internal membrane or crude membrane) content of alpha2 and alpha1 isoforms from the CLP group was significantly increased compared with the sham group 24 hours after operation (P<.05). CONCLUSIONS: Na(+)-K(+) ATPase activity increases 24 hours after CLP in gastrocnemius muscle and then declines. This increase is caused by increased Na(+)-K(+) ATPase protein levels in the plasma membrane.

Animals↗
PubMed2000

Effect of carticaine on the sarcoplasmic reticulum Ca2+-dependent adenosine triphosphatase.

The sarcoplasmic reticulum Ca2+-ATPase (calcium-dependent adenosine triphosphatase) transports Ca2+ from the myoplasm to the reticulum lumen at the expense of free energy from ATP hydrolysis. Carticaine is a local anesthetic of frequent use in dentistry which is now entering other clinical fields. We studied the action of carticaine on the sarcoplasmic reticulum (SR) skeletal muscle Ca2+-ATPase. SR vesicles from rabbit fast skeletal muscle were used. Carticaine inhibits the enzymatic activity. The inhibition of the enzymatic activity depends on pH, [Ca2+] and the presence of calcimycin. Half-maximal carticaine concentration that inhibits the ATPase activity tends to a maximal value upon increasing [Ca2+]. Carticaine concentrations required to inhibit the enzymatic activity at myoplasmic calcium concentration are lower than usual clinical doses: Ki=6.0+/-1.4 mM carticaine (n=5) for 0.1 microM [Ca2+]. ATP-dependent calcium uptake is also inhibited by the local anesthetic: Ki=30.5+/-3.4 mM (n=4). Besides, carticaine inhibits the phosphorylation of the enzyme by inorganic phosphate (Pi): Ki=20.0+/-3.4 (n=5) - 33.2+/-4.6 (n=4) mM, for [Pi] 1-4 mM. Carticaine increases the membrane permeability to Ca2+. Ca2+ efflux from preloaded vesicles is prevented by Ca2+ and Mg2+. Our results suggest that the diffusion of the local anesthetic into muscle fibers might trigger undesired effects such as sustained contraction of the masticatory muscles.

Anesthetics, Local↗
PubMed1982

A simple method for the purification of rat brain Na+,K+-adenosine triphosphatase (ATPase).

Several methods of purification of Na+,K+-adenosine triphosphatase (ATPase) have been previously described for a wide variety of tissues. In general, highest activity preparations have necessitated large amounts of tissue and many purification steps. This article describes a technique that allows partial purification of Na+,K+-ATPase from as few as 15 rat brains and should be of interest to investigators of the pharmacology of this particular enzyme system. In this modified version of the Jorgensen procedure (Biochim Biophys Acta 356:36--52, 1974) we purified the Na+,K+-ATPase from 15--90 rat brains, and obtained enzyme preparations with a mean specific activity of 552 +/- 37.6 mumol Pi/mg of protein/hr (95.5% ouabain sensitive). This "purified" enzyme had an activity ratio (Mg2+ + Na+ + K+)/(Mg2+ + Na+) of 47.4 +/- 12.3 SEM, compared to 3.29 +/- 0.17 SEM for the untreated microsomes. Ouabain inhibited the "purified" enzyme with an I50 of 6 X 10(-9) M. Ouabain binding (644 pmol/mg of protein) yielded a turnover number of 13,700 min-1. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis of the enzyme revealed predominantly the alpha and beta subunits with some minor contaminant bands. Previous methods of purification of rat brain Na+,K+-ATPase have employed sodium deoxycholate and high concentrations of NaI; the reported specific activity obtained was generally 150--350 mumol Pi/mg of protein/hr. We have employed higher SDS concentrations than in Jorgensen's technique for rabbit kidney but the procedure is simpler because sucrose gradients are not used. Final wash steps also include 10--20% glycerol in the media. These modifications have yielded Na+,K+-ATPase of significantly higher specific activity than previously reported for rat brain.

Animals↗
PubMed1980

A cross-linking study of the Ca2+, Mg2+-activated adenosine triphosphatase of Escherichia coli.

The solubilized Ca2+,Mg2+-activated adenosine triphosphatase of Escherichia coli is composed of five subunits designated alpha, beta, gamma, delta and epsilon in order of decreasing molecular weight. The subunit structure of the enzyme has been investigated by the use of the cleavable cross-linking agents dithiobis(succinimidyl propionate), methyl-4-mercaptobutyrimidate, dimethyl-3,3'-dithiobispropionimidate, disuccinimidyl tartarate, and cupric 1,10-phenanthrolinate. The products of cross-linking were analyzed by two different two-dimensional gel electrophoresis systems. The following cross-linked subunit dimers were observed: alpha 2, beta 2, alpha beta, alpha delta, beta gamma, beta delta, beta epsilon and gamma epsilon. These results, together with other published data, are discussed in relation to a model of the arrangement of the subunits in the ATPase molecule.

Ampholyte Mixtures↗
PubMed1990

Characteristics of the H(+)-translocating adenosine triphosphatase of Vibrio parahaemolyticus.

We have characterized H(+)-translocating adenosine triphosphatase (ATPase) in membrane vesicles of Vibrio parahaemolyticus. The ATPase required high concentrations (about 0.5 M) of Na2SO4 (or other salts) for its maximum activity. Magnesium ion stimulated the ATPase activity, but Ca2+ did not. The activity of ATPase was inhibited by tetrachlorosalicylanilide, an H+ conductor, but not by another H+ conductor, carbonylcyanide-m-chlorophenylhydrazone. The activity was strongly inhibited by dicyclohexylcarbodiimide or Zn2+, and partially inhibited by azide, but not at all by vanadate.

Cell Membrane↗