Reversal of decreased phosphorylation of sarcoplasmic reticulum calcium transport ATPase by 1,25-dihydroxycholecalciferol in experimental uremia

1983 ◽  
Vol 35 (1) ◽  
pp. 195-201 ◽  
Author(s):  
Ricardo Boland ◽  
Clifford Matthews ◽  
Ana R. de Boland ◽  
Eberhard Ritz ◽  
Wilhelm Hasselbach
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Transport Atpase ◽  
Sarcoplasmic Reticulum Calcium

A Conformational Transition of the Sarcoplasmic Reticulum Calcium Transport ATPase Induced by Vanadate

1983 ◽  
Vol 38 (11-12) ◽  
pp. 1015-1022 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Pankaj Medda ◽  
Andrea Migala ◽  
Bruno Agostini
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Sites ◽  
Calcium Binding ◽  
Calcium Transport ◽  
Conformational Transition ◽  
Transport Atpase ◽  
Calcium Binding Sites ◽  
Protein Particles ◽  
Sarcoplasmic Reticulum Calcium ◽  
Internal Calcium

Vanadate binding to sarcoplasmic reticulum vesicles results in the loss of the externally located high affinity calcium binding sites of the calcium transport ATPase. Conversely the occupation by calcium of the internally located low affinity sites in the vanadate enzyme complex leads to the release of vanadate. Since the total number of calcium binding sites is not diminished by vanadate binding but slightly increases we conclude that vanadate binding induces a transition of the enzymes external high to internal low affinity calcium binding sites. The transposition of external to internal calcium binding sites is accompanied by a definite change in the structure of the sarcoplasmic reticulum membranes. On vanadate binding the asymmetrically arranged electron dense protein particles become symmetrically distributed

Inactivation of the Sarcoplasmic Reticulum Calcium -Transport-ATPase by Lasolocid in Combination with Triton X-100

1982 ◽  
Vol 37 (11-12) ◽  
pp. 1290-1292
Author(s):  
Wilhelm Hasselbach ◽  
Hans Lüdi ◽  
Andrea Migala
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Critical Micellar Concentration ◽  
Transport Atpase ◽  
Inactive State ◽  
Rapid Inactivation ◽  
Combined Action ◽  
Triton X ◽  
Sarcoplasmic Reticulum Calcium

Abstract The calcium-transport-ATPase of the sarcoplasmic reti­culum membranes is irreversibly inactivated by the combined action of Lasolocid and Triton X-100 at concentrations which separately do not interfere with the enzyme's activity. In the presence of Lasolocid the enzyme is most susceptable to inactivation when the Triton X-100 concentration just exceeds its critical micellar concentration, ~ 0.2 mg · ml-1. Lasolocid becomes effective at a concentration of 10 μᴍ and produces rapid inactivation at 100 μᴍ . The enzyme is more rapidly inactivated in the active than in the inactive state.

Pressure Effects on the Interactions of the Sarcoplasmic Reticulum Calcium Transport Enzyme with Calcium and para-Nitrophenyl Phosphate

1987 ◽  
Vol 42 (5) ◽  
pp. 641-652 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Lore Stephan
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Activation Volume ◽  
Reaction Scheme ◽  
Pressure Effects ◽  
Calcium Dependent ◽  
Nitrophenyl Phosphate ◽  
Hydrolysis Of ◽  
Sarcoplasmic Reticulum Calcium ◽  
Effect Of Hydrostatic Pressure

The effect of hydrostatic pressure on calcium dependent p-nitrophenyl phosphate hydrolysis of the sarcoplasmic reticulum calcium transport enzyme has been investigated at different degree of enzyme saturation by calcium and Mg-p-nitrophenyl phosphate to distinguish between activation and binding volumes. The enzyme saturated by both ligands displays a significant dependence of the activation volume on pressure, rising from 20 ml/mol at atmospheric pressure (0.1 MPa) to 80 ml/mol at 100 MPa. At subsaturating concentration of Mg-p-nitrophenyl phosphate an activation volume of 35 ml/mol prevails between 0.1 and 40 MPa. At subsaturating concentration of calcium the activation volume approximates 80 ml/mol in the same pressure range. The binding volume for both substrates is likewise pressure dependent falling from 20 ml/mol to 0 ml/mol for Mg-p-nitrophenyl phosphate and rising from 67 ml/mol to 155 ml/mol for calcium. The pressure dependence of activation and binding volumes is analysed on account of a simplified reaction scheme yielding activation volumes and rate constants for individual reaction steps.

Low Affinity Calcium Binding Sites of the Calcium Transport ATPase of Sarcoplasmic Reticulum Membranes

1980 ◽  
Vol 35 (11-12) ◽  
pp. 1012-1018 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Vera Koenig
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Sites ◽  
Calcium Binding ◽  
Calcium Transport ◽  
External Surface ◽  
Transport Atpase ◽  
Affinity Constants ◽  
Calcium Binding Sites ◽  
Short Time

Calcium binding sites having low affinity constants of < 103 ᴍ-1 were titrated in native sarcoplasmic reticulum vesicles as well as in lipid deprived membranes and in the isolated calcium transport ATPase. Short time calcium binding measurements and the determination of the calcium binding heat allow to distinguish low affinity calcium binding sites located on the external surface of the sarcoplasmic reticulum membranes from those present in the section of the transport molecule directed to the vesicular space. The same number of internal binding sites was found for preparations deprived of their lipid content as well as of preparations depleted of their lipids and of their accessorial proteins. Magnesium interferes with calcium binding to the external as well as to the internal low affinity calcium binding sites. The implications of the existence of the low affinity calcium binding sites in the internal section of the calcium transport ATPase are discussed.

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