Binding of Ca2+ to phosphoinositols, phosphatidylserines and gangliosides.
The effect of K+, Mg2+ and serotonin on the interaction between Ca2+ and different phospholipids as well as glycosphingolipids (gangliosides) was studied by equilibrium dialysis using 45Ca as tracer. The highly polar phosphatidylinositol-4,5-bisphosphate (TPI) was found to bind more Ca2+ per lipid molecule than all other lipids tested and Ca2+ could not be released as easily as in the other lipids by K+, Mg2+ and serotonin. Ca2+ is released from all lipid-Ca2+ complexes most effectively by Mg2+, serotonin is less effective but enhances K+ in its capacity to displace Ca2+ from the respective binding sites. A remarkable dissociating influence of serotonin on ganglioside-Ca2+ and phosphatidylserine-Ca2+ complexes is observed. This effect is less pronounced with phosphatidylinositol-Ca2+ complexes under comparable comparable conditions. The possible functional role of phospholipids and gangliosides in vivo is discussed with regard to the specific Ca2+-binding properties of these lipids.
D002118:Calcium / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology
D005732:Gangliosides; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D012701:Serotonin; D008274:Magnesium; D011188:Potassium; D002118:Calcium