人及小鼠肝细胞膜载脂蛋白 CⅢ受体的研究

Study of apoC Ⅲ-Binding Sites of Human and Mouse Hepatic Plasma Membranes

用^(125)I 标记载脂蛋白 CⅢ (apoCⅢ)为配体,采用聚乙二醇沉淀分离法,建立了小鼠肝细胞膜 apoCⅢ 受体(结合位点)放射分析法,并对人及小鼠肝细胞膜 apoCⅢ结合位点的特性进行了研究.

A specific,sensitive and simple radioligand binding assay for apoCⅢ-binding sites of hepatic plas-ma membranes has been established by separation of B/F with PEG.Addition of increasing concentra-tion of ^(125)Ⅰ-labeled apoCⅢ to human hepatic plasma membranes revealed saturation binding to mem-branes with a K_d of 0.31μmol/L(3.1×10^(-7)mol/L)and binding maximum of 1.74μg/mg of membraneprotein.In displacement studies using unlabeled apoCⅢ and isolated lipoproteins HDL,LDL andVLDL,only apoCⅢ and VLDL effectively competed with ^(125)Ⅰ-apoCⅢ for membrane binding sites.Thebinding of ^(125)Ⅰ-apoCⅢto human liver plasma membranes was Ca^(2+)-independent and was abolished whenplasma membranes were treated with trypsin.The characteristics of apoCⅢ-binding sites of mouse liv-er plasma membranes was similar to that of human liver plasma membranes with an exception of bindingmaximum of 1.52/μg/mg of membrane protein.