title: Conformation change of the intestinal calcium-binding protein induced by phospholipids in the presence and absence of Ca2+.
abstract: Effects of phospholipids (PL's) and lyso-PL's on the conformation of the porcine intestinal calcium-binding protein (CaBP) were studied fluorometrically with 1-(dimethylamino)naphthalene-5-sulfonyl-(DNS-) labeled CaBP. The fluorescence intensity of DNS-labeled CaBP was much higher in the presence of excess EGTA than in its Ca2+-bound state. In the absence of free Ca2+ (with 1 mM EGTA) the fluorescence of the labeled CaBP was greatly enhanced by addition of lysophosphatidylcholine (lyso-PC), lysophosphatidylserine (lyso-PS), or lysophosphatidylinositol (lyso-PI). With addition of 25 microM Ca2+ the enhancement of the fluorescence by these lyso-PL's was depressed; especially that due to lyso-PC became small. Lysophosphatidylethanolamine (lyso-PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylethanolamine (PE), and mono- and dipalmitoylglycerols had no or much less effect on the fluorescence in the presence and absence of Ca2+. Lyso-PC attenuated in a concentration-dependent manner the quenching of the fluorescence of the DNS-CaBP by high temperatures and increase of ionic strength in the presence of EGTA. Lyso-PL's generally protected the CaBP from digestion with proteases in the presence of EGTA. These experimental results suggest that particular lyso-PL's have Ca2+-sensitive interaction with the porcine CaBP and induce conformation change of the CaBP molecules.
authors.affiliation: Research Laboratory for Development of Medicine, School of Pharmacy, Hokuriku University, Ishikawa, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Chiba
authors.forename: T
authors.initials: T
authors.lastname: Mohri
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D007421:Intestine, Small / Q000378:metabolism*; D007700:Kinetics; D008246:Lysophospholipids / Q000494:pharmacology; D009994:Osmolar Concentration; D010743:Phospholipids / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D013552:Swine; D013816:Thermodynamics
chemical_list: D002135:Calcium-Binding Proteins; D008246:Lysophospholipids; D010743:Phospholipids; D004533:Egtazic Acid; D002118:Calcium