Interaction of caldesmon with endoplasmic reticulum membrane: effects on the mobility of phospholipids in the membrane and on the phosphatidylserine base-exchange reaction.
We have previously demonstrated by tryptophan fluorescence the interaction of caldesmon with anionic phospholipid vesicles [Czurylo, Zborowski and Dabrowska (1993) Biochem. J. 291, 403-408]. In the present work we investigated the interaction of caldesmon with natural-membrane (rat liver endoplasmic reticulum) phospholipids by co-sedimentation assay. The results indicate that 1 mol of caldesmon binds approx. 170 mol of membrane phospholipids with a binding affinity constant of 7.3 x 10(6) M-1. The caldesmon-membrane phospholipid complex dissociates with increasing salt concentration and in the presence of Ca2+/calmodulin. As indicated by EPR measurements of membrane lipids labelled with 5-doxyl stearate and TEMPO-phosphatidylethanolamine, binding of caldesmon results in an increase in mobility of the acyl chains (in the region of carbon 5) and a decrease in polar headgroup mobility of phospholipids. Interaction of caldesmon with phospholipids is accompanied by inhibition of phosphatidylethanolamine synthesis via a phospholipid base-exchange reaction, with phosphatidylserine as substrate. This shows that, of the endoplasmic reticulum membrane phospholipids, the main target of caldesmon is phosphatidylserine.
Makowski
P
P
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
Makuch
R
R
Sikorski
A F
AF
Jezierski
A
A
Pikula
S
S
Dabrowska
R
R
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002645:Chickens; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity; D010714:Phosphatidylethanolamines / Q000096:biosynthesis; D010718:Phosphatidylserines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D010743:Phospholipids; D002118:Calcium