This basic science study characterizes the ATP-dependent and independent calcium binding processes in guinea pig cardiac sarcolemma, indicating distinct binding sites.
ATP-dependent calcium binding predominates at low concentrations in guinea pig sarcolemma; leaves open relevance to human cardiac calcium regulation.
The relationship between calcium binding and ATPase activity has been investigated for guinea pig cardiac sarcolemma. The concentrations of calcium ions and of ATP were the main factors in determining the amount of calcium bound. With a saturating concentration of ATP, at low calcium concentrations (0.1 mM) more than 50% of the total calcium bound was ATP dependent while at high concentrations of calcium (10 mM) only 20% of the calcium bound was ATP dependent. The ATP-dependent calcium binding process involves one class of calcium binding sites while the non-ATP-dependent calcium binding process involves two classes of binding sites. Inhibitor studies of Ca2+-stimulated MgATPase, MgATPase, and CaATPase activities suggest Ca2+ and Mg2+ are either interacting with different sites on the same enzyme or with different enzymes.
No takes yet. Share an insight, caveat, or question.
Morcos et al. (1979) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: