Tegoni M, Spinelli S, Verhoeyen M, Davis P, Cambillau C
Architecture et Fonction des Macromolécules Biologiques UPR 9039, CNRS, IFR1, 31 Chemin Joseph Aiguier, Marseille Cedex 20, 13402, France.
J Mol Biol. 1999 Jun 25;289(5):1375-85. doi: 10.1006/jmbi.1999.2845.
Human chorionic gonadotropin (hCG), is a placental hormone which exerts its major effect by stimulating progesterone production, crucially sustaining the early weeks of pregnancy. Detection of hCG with specific monoclonal antibodies (mAbs) has become the chosen means for pregnancy diagnosis. We have used antibody Fv fragments derived from two high-affinity mAbs, one against the alpha and the other against the beta-hCG subunit to enable the crystallisation of intact or desialylated hCG. Crystals of a ternary complex composed of Fv anti-alpha/hCG/Fv anti-beta were found to diffract to 3.5 A resolution, and the structure was solved by molecular replacement. In the crystal, the two Fvs keep hCG as in a molecular cage, providing good protein-protein contacts and leaving enough space for the saccharides to be accommodated in the cell solvent. The two Fvs were found not to interact directly through their complementary-determining regions with the hCG saccharides, but only with the protein. The hCG structure in the ternary complex was very close to that of the HF partially deglycosylated hormone, thus indicating that neither the saccharides nor the Fvs had any substantial influence on hormone structure.
人绒毛膜促性腺激素（hCG）是一种胎盘激素，其主要作用是刺激孕酮的产生，对维持妊娠早期起着至关重要的作用。用特异性单克隆抗体（mAb）检测hCG已成为妊娠诊断的首选方法。我们使用了源自两种高亲和力单克隆抗体的抗体Fv片段，一种针对α亚基，另一种针对β-hCG亚基，以实现完整或去唾液酸化hCG的结晶。由抗α Fv/hCG/抗β Fv组成的三元复合物晶体的衍射分辨率达到3.5埃，其结构通过分子置换法解析。在晶体中，两个Fv将hCG保持在分子笼中，提供了良好的蛋白质-蛋白质接触，并为糖类在细胞溶剂中容纳留出了足够的空间。发现这两个Fv并非通过其互补决定区直接与hCG糖类相互作用，而仅与蛋白质相互作用。三元复合物中的hCG结构与部分去糖基化的HF激素的结构非常接近，因此表明糖类和Fv对激素结构均无实质性影响。
