Purification and characterization of chicken lipoprotein receptor

(I)用超离心法（d<1.019），将鸡血浆中的乳糜微粒和极低密度脂蛋白（VLDL）与鸡脂蛋白脂蛋白（LPL）在37 ℃孵育2 h，制备出鸡体内的乳糜微粒和VLDL。(2)乳糜微粒残留物和VLDL残留物在Bio-Gel A50 m柱上的洗脱模式几乎为单峰结果表明，鸡胆渣中甘油三酯含量低，胆固醇含量高，载脂蛋白B 100和载脂蛋白A-100含量基本相当，但其胆固醇含量和载脂蛋白A-100的含量基本相当，而载脂蛋白B 100和载脂蛋白A-100的含量基本相当。载脂蛋白C、载脂蛋白52 kDa和载脂蛋白20 kDa含量低于乳糜微粒和VLDL。(3)碘<125>标记的低密度脂蛋白、乳糜微粒残体和极低密度脂蛋白残体与鸡或大鼠肝细胞膜特异性结合。乳糜<I25>微粒、VLDL、VLDL残基或LDL对鸡~（131）I标记LDL与鸡肝膜的特异性结合抑制率均大于70%，而乳糜微粒残基的加入对鸡~（131）I标记LDL与鸡肝膜的特异性结合几乎没有影响。这些结果表明，鸡乳糜微粒残体与LDL不同受体结合。(4)过量<I25>的相应脂蛋白可使鸡原代肝细胞对Chicken 13 I标记脂蛋白的摄取降低至&gt;30%。结果表明，鸡对脂蛋白的摄取是由脂蛋白受体介导的。(5)在鸡肝脂蛋白受体的配体印迹分析中，发现有3种不同的受体蛋白（145、115和105 kDa）存在于鸡肝中。(6)用羟基磷灰石层析、LDL亲和层析和Mono Q层析三步纯化了两种鸡肝脂蛋白受体（CHBR-1和CHBR-2），经SDS-PAGE测定，其分子量分别为115 kDa和105 kDa，经配体印迹分析，CHBR-1和CHBR-2均与载脂蛋白B结合。

(I) Chylomicron remnant and VLDL remnant in chickens were prepared by the method using ultracentrifugation (d<1.019) following an in vitro incubation of chylomicron or VLDL prepared from chicken plasma with chicken LPL for 2h at 37ﾟC.(2) The chylomicron remnants and VLDL remnants yielded the almost single peak in the elution pattern on Bio-Gel A50m column (1.6 * 50cm) and the particle size were smaller than chylomicron and VLDL since the elution of remnants by Bio-Gel A50m was similar to LDL rather than chylomicron and VLDL.Chicken remnants had low triglyceride contents with high cholesterol and almost comparable Apo B100 and Apo A-I contents while lower Apo C,Apo 52kDa and Apo 20kDa contents compared to chylomicron or VLDL.(3) ^<125>I-labeled LDL,chylomicron remnant and VLDL remnant bound specificity to chicken or rat liver membranes. The specific binding of chicken ^<I25>I-labeled LDL to chicken liver membrane was inhibited by >70% with chylomicron, VLDL,VLDL remnant or LDL,while the addition of chylomicron remnant had little effect. These results demonstrate that chicken chylomicron remnant bind the site of different receptor of LDL.(4) The uptake of Chicken ^<I25>I-labeled lipoproteins to chicken primary hepatocyte was decreased to about>30% by an excess of the corresponding lipoproteins. It is concluded that the uptake of chicken lipoproteins are mediated by lipoprotein receptors.(5) In ligand blot aunalysis of chicken hepatic lipoprotein receptors, three difrerent receptor proteins (145,115 and 105 kDa) were present in chicken liver.(6) Two kinds of chicken hepatic lipoprotein receptors were purifed by a procedure with three chromatography step on Hydroxyapatite, LDL-affinity and Mono Q.The receptors (chicken hepatic apo B receptor (CHBR) -1 and CHBR-2) were characterized a molecular weight of 115kDa and 105kDa, as estimated on SDS-PAGE.On ligand blotting, both CHBR-1 and CHBR-2 bound to apo B lipoproteins.