title: Calcium binding and ATPase activities of heart sarcolemma.
abstract: Rat heart sarcolemma prepared by the hypotonic shock-LiBr treatment method was found to bind calcium by a concentration-dependent and saturable process. The calcium binding values at 50 muM and 1.25 mM Ca2+ concentrations were about 30 and 250 nmoles/mg protein, respectively. Both Mg2+ and ATP inhibited calcium binding and no evidence for energy-linked calcium binding with sarcolemmn was found. z sn the other hand, maximal ATP hydrolysis by heart sarcolemma was seen at 4 mM Mg2+ or Ca2+. The Ca2+-ATPase LEO) of Ca2+ failed to stimulate ATP hydrolysis in the presence of various concentrations of Mg-ATP. These results indicate the absence of a "calcium pump" mechanism in the heart sarcolemmal membrane preparation employed in this study.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D012508:Sarcolemma / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*
chemical_list: D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium