scholarly journals Chemical modification of sarcoplasmic reticulum. Stimulation of Ca2+ release

1986 ◽  
Vol 240 (2) ◽  
pp. 509-517 ◽  
Author(s):  
V Shoshan-Barmatz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Acetic Anhydride ◽  
Atpase Activity ◽  
Chemical Modification ◽  
Amino Groups ◽  
Reactive Group ◽  
Rapid Release ◽  
Sarcoplasmic Reticulum Membrane ◽  
Positively Charged ◽  
Stimulation Of

Pretreatment of sarcoplasmic membranes with acetic or maleic anhydrides, which interact principally with amino groups, resulted in an inhibition of Ca2+ accumulation and ATPase activity. The presence of ATP, ADP or adenosine 5′-[beta, gamma-imido]triphosphate in the modification medium selectively protected against the inactivation of ATPase activity by the anhydride but did not protect against the inhibition of Ca2+ accumulation. Acetic anhydride modification in the presence of ATP appeared to increase specifically the permeability of the sarcoplasmic reticulum membrane to Ca2+ but not to sucrose, Tris, Na+ or Pi. The chemical modification stimulated a rapid release of Ca2+ from sarcoplasmic reticulum vesicles passively or actively loaded with calcium, from liposomes reconstituted with the partially purified ATPase fraction but not from those reconstituted with the purified ATPase. The inactivation of Ca2+ accumulation by acetic anhydride (in the presence of ATP) was rapid and strongly pH-dependent with an estimated pK value above 8.3 for the reactive group(s). The negatively charged reagents pyridoxal 5-phosphate and trinitrobenzene-sulphonate, which also interact with amino groups, did not stimulate Ca2+ release. Since these reagents do not penetrate the sarcoplasmic reticulum membranes, it is proposed that Ca2+ release is promoted by modification of internally located, positively charged amino group(s).

scholarly journals Chemical modification of sarcoplasmic reticulum with methylbenzimidate. Stimulation of Ca2+ efflux

1987 ◽  
Vol 243 (1) ◽  
pp. 165-173 ◽  
Author(s):  
V Shoshan-Barmatz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Chemical Modification ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Protein Factor ◽  
Time Period ◽  
Fold Stimulation ◽  
Stimulation Of

Treatment of sarcoplasmic reticulum membranes with 12 mM-methylbenzimidate (MBI) for 5 min, in the presence of 5 mM-ATP at pH 8.5, resulted in a 2-3-fold stimulation of ATP hydrolysis and over 90% inhibition of Ca2+ accumulation. This phenomenon was strictly dependent upon the presence of nucleotides with the following order of effectiveness: adenosine 5′-[beta, gamma-imido]triphosphate greater than or equal to ATP greater than UTP greater than ADP greater than AMP. Divalent cations such as Ca2+, Mg2+ and Mn2+, when present during the MBI treatment, prevented both the stimulation of ATPase activity and the inhibition of Ca2+ accumulation. Modification with MBI had no effect on E-P formation from ATP, ADP-ATP exchange, Ca2+ binding or ATP-Pi exchange catalysed by the membranes. Membranes modified with MBI in the presence of ATP and then passively loaded with Ca2+ released about 80% of their Ca2+ content within 3 s. Control membranes released only 3% of their Ca2+ during the same time period. MBI modification inhibited Ca2+ accumulation by proteoliposomes reconstituted with the partially purified ATPase but not with the purified ATPase fraction. These results suggest that MBI in the presence of ATP stimulates Ca2+ release by modifying a protein factor(s) other than the (Ca2+ + Mg2+)-ATPase.

scholarly journals ATP-dependent interaction of propranolol and local anaesthetic with sarcoplasmic reticulum. Stimulation of Ca2+ efflux

1988 ◽  
Vol 256 (3) ◽  
pp. 733-739 ◽  
Author(s):  
V Shoshan-Barmatz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Local Anaesthetics ◽  
Inhibitory Effect ◽  
Phospholipid Bilayer ◽  
Drug Induced ◽  
Protein Factor ◽  
Dependent Inhibition ◽  
Drug Modification ◽  
Stimulation Of

Preincubation of sarcoplasmic reticulum (SR) with propranolol or tetracaine inhibits Ca2+ accumulation and stimulates ATPase activity by more than 2-fold. This effect is obtained only when the preincubation is carried out in the presence of ATP or other nucleoside triphosphates. The (ATP + drug)-induced inhibition of Ca2+ accumulation is pH-dependent, increasing as the pH rises above 7.5. The presence of micromolar concentrations of Ca2+ or Mg2+ during the preincubation prevents the inhibitory effect of ATP plus drug on Ca2+ accumulation or ATPase activity. The (ATP + drug) modification of SR vesicles resulted in stimulation of a rapid Ca2+ efflux from passively loaded vesicles. The ATP-dependent inhibition of Ca2+ accumulation by the drug is obtained with other local anaesthetics. The drug concentration required for 50% inhibition was 0.15 mM for dibucaine and 0.4 mM for both propranolol and tetracaine, whereas it was 5 mM, 8 mM and greater than 10 mM for lidocaine, benzocaine and procaine respectively. The heavy SR vesicles were only slightly affected by the incubation with propranolol or tetracaine in the presence of ATP, but their sensitivity increased markedly after storage at 0 degrees C for 24-48 h. These results suggest that propranolol and some local anaesthetics, in the presence of ATP, stimulate Ca2+ efflux by modifying a protein factor(s) rather than the phospholipid bilayer.

scholarly journals Effect of Heptane Treatment on the Response of Sarcoplasmic Reticulum Preparations to Phosphate

1976 ◽  
Vol 29 (6) ◽  
pp. 459
Author(s):  
Douglas J Horgan
Keyword(s):  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Binding Sites ◽  
Calcium Uptake ◽  
Straight Line ◽  
Enzyme Intermediates ◽  
Stimulation Of ◽  
Linear Shape ◽  
Burk Plot

The calcium-stimulated (extra) ATPase and calcium uptake activities of sarcoplasmic reticulum (SR) preparations treated with aqueous heptane mixtures were compared with those of untreated SR, and with those of SR treated with aqueous ether. Both treatments altered the kinetic behaviour of the extra ATPase, the Lineweaver-Burk plot being changed from its normal non-linear shape to a straight line. Kinetic constants, Vma ., Km for ATP and KI for phosphate, were measured. The extra ATPase activity of heptane-treated SR was inhibited by phosphate as was that of ether-treated SR, to a lesser extent. The magnitude of this inhibition by phosphate was found to be considerably less than the degree of stimulation of the extra ATPase activity of untreated SR caused by phosphate through its calcium-precipitating action. The steady-state concentrations of the phosphoryl-enzyme intermediates were measured and together with the K m and K, values they indicate that the binding of ATP to heptane-treated SR is weaker than it is to untreated SR, and that phosphate is an efficient competitor for the binding sites.

Electron Microscopic Evidence for the Transmembrane Displa cement of Calcium ATPase

1984 ◽  
Vol 39 (1-2) ◽  
pp. 177-179 ◽  
Author(s):  
Donald J. Scales ◽  
Stefan R. Highsmith
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Freeze Fracture ◽  
Calcium Atpase ◽  
Two Dimensional ◽  
Electron Microscopic ◽  
Microscopic Evidence ◽  
Sarcoplasmic Reticulum Membrane ◽  
First Time

Abstract Incubation of the Ca2+-ATPase in vanadate solutions leads to the formation of two-dimensional arrays in the sarcoplasmic reticulum membrane. Electron micrographic freeze fracture replicas show depressions on the inner leaflet for the first time. This indicates that the ATPase has moved perpendicular to the plane of the membrane. Our results also suggest that aggregation of the Ca2+-ATPase into the two-dimensional arrays occurs before they move into the membrane. These phenomena were observed as soon as 15 minutes after vanadate was added. The effects of vanadate appear to be completely reversible. When SR was incubated in the vanadate solutions and was then diluted into a buffer containing Ca2+ and ATP, the ATPase activity was normal for up to several hours of incubation and only somewhat reduced after 3 days.

scholarly journals The effect of dantrolene on skeletal-muscle sarcoplasmic-reticulum function in malignant hyperpyrexia in pigs

1983 ◽  
Vol 212 (2) ◽  
pp. 399-405 ◽  
Author(s):  
M D White ◽  
J G Collins ◽  
M A Denborough
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Muscle Relaxant ◽  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Polyacrylamide Gel ◽  
Malignant Hyperpyrexia ◽  
Dependent Atpase ◽  
Sarcoplasmic Reticulum Membrane

The effect of the muscle relaxant dantrolene on isolated sarcoplasmic reticulum was studied in control and malignant-hyperpyrexia-susceptible Landrace pigs. The membranes prepared from both sources showed similar Ca2+-dependent ATPase activities, had comparable phospholipid/protein ratios, and their sodium dodecyl sulphate/polyacrylamide-gel patterns were indistinguishable. Membranes from both sources appeared to bind similar amounts of dantrolene. The drug did not stimulate Ca2+-dependent ATPase activity in preparations from either source. The rates of Ca2+ exchange and Ca2+ efflux appeared to be similar in sarcoplasmic reticulum of control and malignant-hyperpyrexia-susceptible pigs. Dantrolene did not affect either the rates or the amount of Ca2+ lost from the vesicles. These results suggest that dantrolene does not directly affect the movement of Ca2+ across the sarcoplasmic-reticulum membrane.

scholarly journals Stimulation of Ca2+ efflux from sarcoplasmic reticulum by preincubation with ATP and inorganic phosphate

1987 ◽  
Vol 247 (3) ◽  
pp. 497-504 ◽  
Author(s):  
V Shoshan-Barmatz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Inorganic Phosphate ◽  
Catalytic Cycle ◽  
Photoaffinity Labelling ◽  
Ph Dependent ◽  
Specific Labelling ◽  
Stimulation Of

Preincubation of sarcoplasmic reticulum with 1 mM-ATP completely inhibits Ca2+ accumulation and stimulates ATPase activity by over 2-fold. This effect of ATP is obtained only when the preincubation is carried out in the presence of Pi, but not with arsenate, chloride or sulphate. The inhibition by ATP of Ca2+ accumulation is pH-dependent, increasing as the pH is increased above 7.5. Inhibition of Ca2+ accumulation is observed on preincubation with ATP, but not with CTP, UTP, GTP, ADP, adenosine 5′-[beta gamma-methylene]triphosphate or adenosine 5′-[beta gamma-imido]triphosphate. The presence of Ca2+, but not Mg2+, during the preincubation, prevents the effect of ATP + Pi on Ca2+ accumulation. The ATP + Pi inhibition of Ca2+ accumulation is not due to modification of the ATPase catalytic cycle, but rather to stimulation of a rapid Ca2+ efflux from actively or passively loaded vesicles. This Ca2+ efflux is inhibited by dicyclohexylcarbodi-imide. Photoaffinity labelling of sarcoplasmic-reticulum membranes with 8-azido-[alpha-32P]ATP resulted in specific labelling of two proteins, of approx. 160 and 44 kDa. These proteins were labelled in the presence of Pi, but not other anions.

scholarly journals Stimulation of the Ca2+-ATPase of sarcoplasmic reticulum by disulfiram

1996 ◽  
Vol 320 (1) ◽  
pp. 101-105 ◽  
Author(s):  
Anthony P STARLING ◽  
J. Malcolm EAST ◽  
Anthony G LEE
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Binding Site ◽  
Equilibrium Constant ◽  
Nucleotide Binding ◽  
Nucleotide Binding Site ◽  
Single Site ◽  
Stimulation Of

Disulfiram [bis(diethylthiocarbamoyl)disulphide] has been found to stimulate reversibly the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum. At pH 7.2, 2.1 mM ATP and 25 °C, ATPase activity was found to double on addition of 120 µM disulfiram. Stimulation fitted to binding of disulfiram at a single site with a Kd of 61 µM. Disulfiram had no effect on the Ca2+ affinity of the ATPase or on the rate of phosphorylation of the ATPase by ATP, but increased the rate of dissociation of Ca2+ from the phosphorylated ATPase (the transport step) and increased the rate of dephosphorylation of the phosphorylated ATPase. It also decreased the level of phosphorylation of the ATPase by Pi, consistent with a 7.5-fold decrease in the equilibrium constant of the phosphorylated to non-phosphorylated forms (E2PMg/E2PiMg) at 80 µM disulfiram. Disulfiram had no significant effect on the concentration of ATP resulting in stimulation of ATPase activity, suggesting that it does not bind to the empty nucleotide-binding site on the phosphorylated ATPase. Studies of the effects of mixtures of disulfiram and jasmone (another molecule that stimulates the ATPase) suggest that they bind to separate sites on the ATPase.

scholarly journals Chemical modification studies on a lectin from winged-bean [Psophocarpus tetragonolobus (L.) DC] tubers

1988 ◽  
Vol 254 (2) ◽  
pp. 351-357 ◽  
Author(s):  
M S Shet ◽  
M Madaiah
Keyword(s):  
Acetic Anhydride ◽  
Chemical Modification ◽  
Succinic Anhydride ◽  
Structural Changes ◽  
Dicarboxylic Acids ◽  
Winged Bean ◽  
Amino Groups ◽  
Reductive Methylation ◽  
Tryptophan Residues ◽  
Haemagglutinating Activity

The effect of chemical modification on a D(+)-galactose-specific lectin isolated from winged-bean tubers was investigated to identify the type of amino acid involved in its haemagglutinating activity. Various anhydrides of dicarboxylic acids, such as acetic anhydride, succinic anhydride, maleic anhydride and citraconic anhydride, modified 57-68% of the amino groups of the winged-bean tuber lectin. Treatment with N-acetylimidazole modified only 45% of the total amino groups. Reductive methylation of free amino groups modified 57% of the amino groups. Modification of the amino groups of the lectin by acetic anhydride and succinic anhydride did not lead to any significant change in the haemagglutinating activity (greater than or equal to 75% active). However, citraconylation and maleylation of the lectin led to a significant decrease in the haemagglutinating activity (less than or equal to 20% active). Acetylation and succinylation (3-carboxypropionylation) of the lectin led to a decrease in the pI value of the native lectin from approx. 9.5 to approx. 4.5. Treatment of the lectin with N-bromosuccinimide led to the modification of two and four tryptophan residues per molecule in the absence and in the presence of 8 M-urea respectively. The immunological identity of all the modified lectin preparations showed no gross structural changes except the lectin modified with N-bromosuccinimide in the presence of urea at pH 4.0.

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