Volanakis J E, Narkates A J
J Immunol. 1981 May;126(5):1820-5.
We have examined the interaction of C-reactive protein (CRP) with model membranes and complement. Binding of CRP to multilamellar liposomes or unilamellar vesicles of egg-phosphatidylcholine required the presence of lysophosphatide in the bilayer. The binding was Ca++-dependent, could be inhibited by phosphocholine, and resulted in activation of the classical complement pathway. A weak interaction between CRP and agarose was observed, which was also CA++-dependent and could be inhibited by phosphocholine and galactose. In addition, incorporation of galactocyl cerebroside in phosphatidylcholine:lysophosphatidylcholine liposomes enhanced the binding of CRP. Binding constants of 1.9 X 10(-5) M and 7.1 X 10(-5) M were calculated for liposomes containing and lacking the glycolipid, respectively. Furthermore, CRP bound to galactocyl cerebroside-containing liposomes bound approximately twice as much C1q as the same amount of CRP bound to liposomes lacking the glycolipid. We conclude that: 1) An alteration of the normal organization of phosphatidylcholine bilayers is necessary for binding of CRP. 2) The presence of galactosyl residues on the surface of the bilayer enhances the binding of CRP, perhaps through interaction with a putative secondary binding site on the protein.
我们研究了C反应蛋白（CRP）与模型膜及补体的相互作用。CRP与多层脂质体或卵磷脂单层囊泡的结合需要双层膜中存在溶血磷脂。这种结合依赖于Ca++，可被磷酸胆碱抑制，并导致经典补体途径的激活。观察到CRP与琼脂糖之间存在微弱相互作用，这种相互作用也依赖于Ca++，并可被磷酸胆碱和半乳糖抑制。此外，在磷脂酰胆碱：溶血磷脂酰胆碱脂质体中加入半乳糖脑苷脂可增强CRP的结合。分别计算了含有和缺乏糖脂的脂质体的结合常数，分别为1.9×10^(-5) M和7.1×10^(-5) M。此外，与含有半乳糖脑苷脂的脂质体结合的CRP结合的C1q量约为与缺乏糖脂的脂质体结合的等量CRP的两倍。我们得出以下结论：1）CRP的结合需要磷脂酰胆碱双层正常组织的改变。2）双层膜表面半乳糖基残基的存在增强了CRP的结合，可能是通过与蛋白质上假定的二级结合位点相互作用实现的。
