Ligand binding characteristics and aggregation behavior of purified cow's milk folate binding protein depends on the presence of amphiphatic substances including cholesterol, phospholipids, and synthetic detergents.

摘要: Folate binding protein was purified from cow's milk by a combination of cation exchange chromatography and methotrexate-AH-sepharose affinity chromatography. Dilution the preparation to concentrations less than 10 nM resulted in drastic changes radioligand (folate) characteristics, i.e., decrease with change upward downward convex Scatchard plots increased ligand dissociation combined appearance weak-affinity aggregated forms on gel filtration. These findings, consistent model predicting dimerization between unliganded liganded monomers, were reversed presence material eluted column after adsorption protein(cofactor) or cholesterol, phospholipids, synthetic detergents. The latter amphiphatic substances form micelles lipid bilayers which could separate hydrophobic monomers hydrophilic surrounding aqueous medium thereby prevent association these monomeric prevailing at low protein. Our data have some bearings studies show that cholesterol phospholipids are necessary for clustering folate receptors cell membrane; process required optimum receptor function internalization folate.