Heparin inhibits the reconstituted plasma membrane Ca(2+)-ATPase from porcine brain synaptosome.
Heparin has been shown to be involved in the regulation of cellular Ca(2+) by binding to many proteins with high affinity. Here we examined the effects of heparin on the plasma membrane Ca(2+)-ATPase from porcine brain synaptosome. Our results showed that heparin dramatically inhibited the ATP hydrolysis and Ca(2+) uptake in the presence and absence of calmodulin. Together with controlled proteolysis by trypsin, we concluded that the calmodulin-binding domain of the plasma membrane Ca(2+)-ATPase was less important for the heparin inhibition. Excess phosphatidylserine was able to eliminate the heparin inhibition. We observed that Ca(2+) affinity kept no obvious changes, but the ATP affinity of plasma membrane Ca(2+)-ATPase was apparently decreased in the presence of heparin. Our results indicated that heparin had little effects on ATP or Ca(2+) binding sites of the enzyme.
Zhao
Yongfang
Y
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
Zhang
Xujia
X
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D006493:Heparin / Q000494:pharmacology*; D007700:Kinetics; D013552:Swine; D013574:Synaptosomes / Q000201:enzymology*
D000255:Adenosine Triphosphate; D006493:Heparin; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium