Naoum H G, De Chazal R C, Eaton B M, Contractor S F
Biochim Biophys Acta. 1987 Aug 20;902(2):193-9. doi: 10.1016/0005-2736(87)90295-1.
The binding characteristics of very-low-density (VLDL), low-density (LDL) and high-density (HDL) lipoprotein fractions to a purified human term placental microvillous membrane preparation were determined. Binding of LDL was saturable with a maximal binding capacity of 270 ng LDL protein per mg of membrane protein. Scatchard analysis revealed the presence of a single population of 3.4 X 10(11) sites per mg of membrane protein and a mean affinity constant of 5.8 X 10(-9) M. Binding of VLDL was also saturable but the maximal capacity was 4.5-times greater than that of LDL. The Scatchard analysis revealed the presence of 2.1 X 10(11) binding sites and an affinity constant nearly one order of magnitude greater than that of LDL. Binding of HDL showed less tendency to saturate. Scatchard analysis showed a similar number of receptor sites to that calculated for VLDL and LDL but the affinity constant for HDL was over 100-fold less than that of VLDL. Self- and cross-inhibition studies of VLDL and LDL binding revealed that VLDL was better at blocking the binding of LDL than was LDL itself. This preferential binding of VLDL suggests that this lipoprotein fraction could be an important source of cholesterol for placental progesterone production.
测定了极低密度（VLDL）、低密度（LDL）和高密度（HDL）脂蛋白组分与纯化的人足月胎盘微绒毛膜制剂的结合特性。LDL的结合具有饱和性，每毫克膜蛋白的最大结合容量为270 ng LDL蛋白。Scatchard分析显示，每毫克膜蛋白存在3.4×10¹¹个单一群体的位点，平均亲和常数为5.8×10⁻⁹ M。VLDL的结合也具有饱和性，但最大容量比LDL大4.5倍。Scatchard分析显示存在2.1×10¹¹个结合位点，亲和常数比LDL大近一个数量级。HDL的结合显示出较低的饱和倾向。Scatchard分析显示，HDL的受体位点数量与VLDL和LDL计算的数量相似，但HDL的亲和常数比VLDL小100倍以上。VLDL和LDL结合的自身和交叉抑制研究表明，VLDL比LDL本身更能有效地阻断LDL的结合。VLDL的这种优先结合表明，这种脂蛋白组分可能是胎盘孕酮产生所需胆固醇的重要来源。
