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 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 The Effect of Calcium Ionophores on Fragmented Sarcoplasmic Reticulum

1972 ◽  
Vol 60 (6) ◽  
pp. 735-749 ◽  
Author(s):  
Antonio Scarpa ◽  
Judith Baldassare ◽  
Giuseppe Inesi
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Electron Microscopic ◽  
Microscopic Appearance ◽  
Calcium Accumulation ◽  
Calcium Dependent ◽  
Dependent Atpase

X-537 A and A 23187, two antibiotics which form liphophilic complexes with divalent cations, function as ionophores in vesicular fragments of sarcoplasmic reticulum (SR). Addition of either ionophore to SR preloaded with calcium in the presence of adenosine triphosphate (ATP), causes rapid release of calcium. Furthermore, net calcium accumulation by SR is prevented, when the ionophores are added to the reaction mixture before ATP. On the contrary, ATP-independent calcium binding to SR is not inhibited. This effect is specific for the two antibiotics and could not be reproduced, either by inactive derivatives, or by other known ionophores. Neither ionophore produces alterations of the electron microscopic appearance of SR membranes or inhibition of the calcium-dependent ATPase. In fact, the burst of ATP hydrolysis obtained on addition of calcium, is prolonged in the presence of the ionophores. Lanthanum inhibits ATP-independent calcium binding to SR, ATP-dependent calcium accumulation and calcium-dependent ATPase. However, addition of lanthanum to SR preloaded in the presence of ATP, does not cause calcium release. The reported experiments indicated that: (a) ATP-dependent calcium accumulation by SR results in primary formation of calcium ion gradients across the membrane. (b) Most of the accumulated calcium is not available for displacement by lanthanum on the outer surface of the membrane. (c) Calcium ionophores induce rapid equilibration of the gradients, by facilitating cation diffusion across the membrane.

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.

Stability of the two wings of the coiled-coil domain of ClpB chaperone is critical for its disaggregation activity

2009 ◽  
Vol 421 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Yo-hei Watanabe ◽  
Yosuke Nakazaki ◽  
Ryoji Suno ◽  
Masasuke Yoshida
Keyword(s):  
Atpase Activity ◽  
Leucine Zipper ◽  
Coiled Coil ◽  
Chaperone Activity ◽  
Aaa Atpase ◽  
Coiled Coil Domain ◽  
Central Pore ◽  
Substrate Proteins ◽  
Fold Stimulation ◽  
Stimulation Of

The ClpB chaperone forms a hexamer ring and rescues aggregated proteins in co-operation with the DnaK system. Each subunit of ClpB has two nucleotide-binding modules, AAA (ATPase associated with various cellular activities)-1 and AAA-2, and an 85-Å (1 Å=0.1 nm)-long coiled-coil. The coiled-coil consists of two halves: wing-1, leaning toward AAA-1, and wing-2, leaning away from all the domains. The coiled-coil is stabilized by leucine zipper-like interactions between leucine and isoleucine residues of two amphipathic α-helices that twist around each other to form each wing. To destabilize the two wings, we developed a series of mutants by replacing these residues with alanine. As the number of replaced residues increased, the chaperone activity was lost and the hexamer became unstable. The mutants, which had a stable hexameric structure but lost the chaperone activities, were able to exert the threading of soluble denatured proteins through their central pore. The destabilization of wing-1, but not wing-2, resulted in a several-fold stimulation of ATPase activity. These results indicate that stability of both wings of the coiled-coil is critical for full functioning of ClpB, but not for the central-pore threading of substrate proteins, and that wing-1 is involved in the communication between AAA-1 and AAA-2.

scholarly journals Participation of a transmembrane proton gradient in 5-hydroxytryptamine transport by platelet dense granules and dense-granule ghosts

1981 ◽  
Vol 198 (1) ◽  
pp. 113-123 ◽  
Author(s):  
J A Wilkins ◽  
L Salganicoff
Keyword(s):  
Steady State ◽  
Atpase Activity ◽  
Biogenic Amine ◽  
Atp Hydrolysis ◽  
Blood Platelets ◽  
Dense Granule ◽  
Proton Gradient ◽  
Dense Granules ◽  
Direct Measurements ◽  
Stimulation Of

Dense granules, the storage organelles for 5-hydroxytryptamine in blood platelets, have been isolated from porcine platelets and are shown to transport 5-hydroxytryptamine in response to a transmembrane proton gradient (delta pH). Transport in the absence of delta pH is minimal, and it is shown that a rapid increase in transport takes place as delta pH increases. Direct measurements with [14C]methylamine show a delta pH of 1.1 units (acid inside) for intact granules. Osmotically active ghosts of dense granules from which 95% of the endogenous 5-hydroxytryptamine content has been released have also been prepared. Ghosts swell in the presence of ATP and Mg2+, and this swelling is shown to be due to the entry of protons via a process linked to ATP hydrolysis. Proton entry is also apparently linked to anion penetration in ghosts. Steady-state 5-hydroxytryptamine transport in ghosts is stimulated approx. 3-fold on the addition of ATP to the incubation medium, and the stimulation of 5-hydroxytryptamine transport in ghosts correlates with the formation of a transmembrane delta pH. Ghosts generate a delta pH of 1.1-1.3 pH units (acid inside) in the presence of 5 mM-ATP/2.5 mM-MgSO4. delta pH is generated within 3 min at 37 degrees C and is dissipated by the ionophore nigericin and by NH4Cl. It is shown that an Mg2+-stimulated ATPase activity is present on the ghost membrane, and inhibition of the ATPase leads to a corresponding decrease in 5-hydroxytryptamine transport. The results presented support the idea that 5-hydroxytryptamine transport into platelet dense granules is dependent on the presence of a transmembrane delta pH and, together with previous findings by others, suggest a generalized mechanism for biogenic amine transport into subcellular storage organelles.

scholarly journals Structural evidence for the roles of divalent cations in actin polymerization and activation of ATP hydrolysis

2018 ◽  
Vol 115 (41) ◽  
pp. 10345-10350 ◽  
Author(s):  
Clement P. M. Scipion ◽  
Umesh Ghoshdastider ◽  
Fernando J. Ferrer ◽  
Tsz-Ying Yuen ◽  
Jantana Wongsantichon ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Actin Polymerization ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Md Simulations ◽  
Cumulative Probability ◽  
X Ray ◽  
Rate Of Hydrolysis ◽  
Protein Components ◽  
Cation Sites

The structure of the actin filament is known at a resolution that has allowed the architecture of protein components to be unambiguously assigned. However, fully understanding the chemistry of the system requires higher resolution to identify the ions and water molecules involved in polymerization and ATP hydrolysis. Here, we find experimental evidence for the association of cations with the surfaces of G-actin in a 2.0-Å resolution X-ray structure of actin bound to a Cordon-Bleu WH2 motif and in previously determined high-resolution X-ray structures. Three of four reoccurring divalent cation sites were stable during molecular dynamics (MD) simulations of the filament, suggesting that these sites may play a functional role in stabilizing the filament. We modeled the water coordination at the ATP-bound Mg2+, which also proved to be stable during the MD simulations. Using this model of the filament with a hydrated ATP-bound Mg2+, we compared the cumulative probability of an activated hydrolytic water molecule approaching the γ-phosphorous of ATP, in comparison with G-actin, in the MD simulations. The cumulative probability increased in F-actin in line with the activation of actin’s ATPase activity on polymerization. However, inclusion of the cations in the filament lowered cumulative probability, suggesting the rate of hydrolysis may be linked to filament flexibility. Together, these data extend the possible roles of Mg2+ in polymerization and the mechanism of polymerization-induced activation of actin’s ATPase activity.

scholarly journals Hyperthyroidism increases the uncoupled ATPase activity and heat production by the sarcoplasmic reticulum Ca2+-ATPase

2003 ◽  
Vol 375 (3) ◽  
pp. 753-760 ◽  
Author(s):  
Ana Paula ARRUDA ◽  
Wagner S. da-SILVA ◽  
Denise P. CARVALHO ◽  
Leopoldo de MEIS
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Heat Production ◽  
Atp Hydrolysis ◽  
Fold Increase ◽  
Heat Sources ◽  
Muscle Type ◽  
Red Muscle

The sarcoplasmic reticulum Ca2+-ATPase is able to modulate the distribution of energy released during ATP hydrolysis, so that a portion of energy is used for Ca2+ transport (coupled ATPase activity) and a portion is converted into heat (uncoupled ATPase activity). In this report it is shown that T4 administration to rabbits promotes an increase in the rates of both the uncoupled ATPase activity and heat production in sarcoplasmic reticulum vesicles, and that the degree of activation varies depending on the muscle type used. In white muscles hyperthyroidism promotes a 0.8-fold increase of the uncoupled ATPase activity and in red muscle a 4-fold increase. The yield of vesicles from hyperthyroid muscles is 3–4-fold larger than that obtained from normal muscles; thus the rate of heat production by the Ca2+-ATPase expressed in terms of g of muscle in hyperthyroidism is increased by a factor of 3.6 in white muscles and 12.0 in red muscles. The data presented suggest that the Ca2+-ATPase uncoupled activity may represent one of the heat sources that contributes to the enhanced thermogenesis noted in hyperthyroidism.

ATP turnover by the fatty acid reductase complex of Photobacterium phosphoreum

1985 ◽  
Vol 63 (10) ◽  
pp. 1106-1111 ◽  
Author(s):  
Angel Rodriguez ◽  
Ivan R. Nabi ◽  
Edward Meighen
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Atp Hydrolysis ◽  
Photobacterium Phosphoreum ◽  
Enzyme Complex ◽  
High Pressure Liquid Chromatographic ◽  
20 Nm ◽  
Liquid Chromatographic ◽  
Fold Stimulation ◽  
Stimulation Of

A sensitive reverse-phase high pressure liquid chromatographic assay for formation of AMP coupled with analysis of aldehyde production has been used to characterize the properties of the fatty acid reductase complex of Photobacterium phosphoreum. The enzyme complex, which consists of three different polypeptides (34 000, 50 000, and 58 000), has a high affinity for ATP (Km = 20 nM) and shows highest specificity with C14 fatty acids. Activation of the fatty acid is efficiently coupled to the reduction step showing a stoichiometry of one molecule of fatty acid reduced to aldehyde and one molecule of NADPH oxidized for every molecule of ATP converted to AMP. Reconstituted fatty acid reductase (50 000 and 58 000) shows an ATP hydrolase activity that is independent of NADPH with the maximum amount of AMP formed limited by the amount of fatty acid in the assay, consistent with acyl-protein turnover experiments and the channeling of fatty acids to form acyl thioesters (−NADPH) or aldehyde (+NADPH). Addition of the 34 000 polypeptide to the reconstituted enzyme results in stimulation of AMP formation (−NADPH) to a level far exceeding the amount of fatty acid, showing that the fatty acid can be recycled by the 34 000 protein through its thioesterase activity. Also the 34 000 protein is responsible for a two- to three-fold stimulation in the rate of ATP hydrolysis, suggesting that it can be involved in the stabilization of the enzyme complex.

scholarly journals The Mechanism of the Action of Caffeine on Sarcoplasmic Reticulum

1968 ◽  
Vol 52 (5) ◽  
pp. 760-772 ◽  
Author(s):  
A. Weber
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Transport System ◽  
Turnover Rate ◽  
Atp Hydrolysis ◽  
Uptake System ◽  
Transport Atpase ◽  
Ca Uptake

Evidence is presented that caffeine does not act on the mitochondrial Ca uptake system and that its effect cannot be attributed to the accumulation of adenosine 3',5'-phosphate. Two distinct caffeine effects are described. At high ATP concentrations caffeine decreases the coupling between ATP hydrolysis and Ca inflow. It either inhibits inflow without any inhibition of the rate of ATP hydrolysis, or it stimulates the ATPase activity without stimulating Ca inflow. These high ATP concentrations (much higher than needed for the saturation of the transport ATPase) greatly reduce the control of the turnover rate of the transport system, by accumulated Ca. At low ATP concentrations when the transport system is under maximal control by accumulated Ca, caffeine inhibits the ATPase activity without affecting the rate of Ca inflow.

Sign in / Sign up

Export Citation Format

Share Document