Stimulatory effect of regucalcin on ATP-dependent calcium transport in rat liver plasma membranes.
The effect of regucalcin, a calcium-binding protein isolated from rat liver cytoplasm, on ATP-dependent calcium transport in the plasma membrane vesicles of rat liver was investigated. (Ca(2+)- Mg2+)-ATPase activity in the liver plasma membranes was significantly increased by the presence of regucalcin (0.1-0.5 microM) in the enzyme reaction mixture. This increase was completely inhibited by the presence of sulfhydryl group modifying reagent Nethylmaleimide (5.0 mM NEM) or digitonin (0.04%), which can solubilize the membranous lipids. When ATP-dependent calcium uptake by liver plasma membrane vesicles was measured by using 45CaCl2, the presence of regucalcin (0.1-0.5 microM) in the reaction mixture caused a significant increase in the 45Ca2+ uptake. This increase was about 2-fold with 0.5 microM regucalcin addition. An appreciable increase was seen by 5 min incubation with regucalcin addition. The regucalcin-enhanced ATP-dependent 45Ca2+ uptake by the plasma membrane vesicles was completely inhibited by the presence of NEM (5.0 mM) or digitonin (0.04%). These results demonstrate that regucalcin activates (Ca(2+)-Mg2+)-ATPase in the liver plasma membranes and that it can stimulate ATP-dependent calcium transport across the plasma membranes.
Takahashi
H
H
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Japan.
Yamaguchi
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D047908:Intracellular Signaling Peptides and Proteins; D017136:Ion Transport; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015238:Sulfotransferases
D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000255:Adenosine Triphosphate; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium