Coupling of Ca2+ transport to ATP hydrolysis by the Ca2+-ATPase of sarcoplasmic reticulum: potential role of the 53-kilodalton glycoprotein.
An essential feature of the function of the Ca2+-ATPase of sarcoplasmic reticulum (SR) is the close coupling between the hydrolysis of ATP and the active transport of Ca2+. The purpose of this study is to investigate the role of other components of the SR membrane in regulating the coupling of Ca2+-ATPase in SR isolated from rabbit skeletal muscle, reconstituted SR, and purified Ca2+-ATPase/phospholipid complexes. Our results suggest that (1) it is possible to systematically alter the degree of coupling obtained in reconstituted SR preparations by varying the [KC1] present during cholate solubilization, (2) the variation in coupling is not due to differences in the permeability of the reconstituted SR vesicles to Ca2+, and (3) vesicles reconstituted with purified Ca2+-ATPase are extensively uncoupled under our experimental conditions regardless of the lipid/protein ratio or phospholipid composition. In reconstituted SR preparations prepared by varying the [KC1] present during cholate treatment, we find a direct correlation between the relative degree of coupling between ATP hydrolysis and Ca2+ transport and the level of the 53-kilodalton (53-kDa) glycoprotein of the SR membrane. These results suggest that the 53-kDa glycoprotein may be involved in regulating the coupling between ATP hydrolysis and Ca2+ transport in the SR.
Leonards
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Kutchai
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D007700:Kinetics; D008563:Membrane Lipids / Q000502:physiology; D009132:Muscles / Q000201:enzymology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013816:Thermodynamics
D006023:Glycoproteins; D008563:Membrane Lipids; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium