CONTROL OF THE CONFORMATIONAL STATES OF THE CALCIUM TRANSPORT ENZYME OF SARCOPLASMIC RETICULUM BY CALCIUM

Mitochondria and sarcoplasmic reticulum (SR) fractions were isolated from exercised-trained (E-T) and sedentary control dog hearts. Measurements of mitochondrial respiratory functions indicated no changes in energy-producing (ATP synthesis) capacity in mitochondria from E-T compared to control dog hearts. However, the ability of isolated mitochondria from E-T hearts to retain accumulated calcium was markedly decreased compared to controls. Inhibition of mitochondrial rates of calcium uptake with the inhibitor, ruthenium red, revealed fewer binding and/or transport sites in mitochondrial membranes from exercised-trained heart preparations. ATP-dependent binding (- oxalate) and uptake (+ oxalate) of calcium by SR preparations from E-T hearts were unchanged compared to controls. In contrast, significant differences in the rates of release of bound calcium were found in SR isolated from E-T hearts. Total myocardial protein, nucleic acids, and connective tissue levels were unchanged in E-T hearts compared to controls. The results suggest subtle changes are occurring in the energy-utilizing mechanism(s) involving calcium transport of the myocardial cell during exercise training. These changes may be related to alterations in the performance of the exercised-trained heart.

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The calcium-sensitive dye arsenazo III inhibits calcium transport and ATP hydrolysis by the sarcoplasmic reticulum calcium pump

Analytical Biochemistry ◽

10.1016/0003-2697(87)90022-4 ◽

1987 ◽

Vol 162 (1) ◽

pp. 160-162 ◽

Cited By ~ 8

Author(s):

Sylvie Riollet ◽

Philippe Champeil

Keyword(s):

Sarcoplasmic Reticulum ◽

Calcium Transport ◽

Atp Hydrolysis ◽

Calcium Pump ◽

Arsenazo Iii ◽

Sarcoplasmic Reticulum Calcium

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

Zeitschrift für Naturforschung C ◽

10.1515/znc-1987-0523 ◽

1987 ◽

Vol 42 (5) ◽

pp. 641-652 ◽

Cited By ~ 14

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.

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