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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of the receptor-binding domain of human thrombopoietin determined by complexation with a neutralizing antibody fragment
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Structure of the receptor-binding domain of human thrombopoietin determined by complexation with a neutralizing antibody fragment

机译:通过与中和抗体片段复合来测定人血小板生成素受体结合域的结构

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摘要

The cytokine thrombopoietin (TPO), the ligand for the hematopoi-etic receptor c-MpI, acts as a primary regulator of megakaryocy-topoiesis and platelet production. We have determined the crystal structure of the receptor-binding domain of human TPO (hTPO_(163)) to a 2.5-A resolution by complexation with a neutralizing Fab fragment. The backbone structure of hTPO_(163) has an antiparallel four-helix bundle fold. The neutralizing Fab mainly recognizes the C-D crossover loop containing the species invariant residue Q111. Titration calorimetric experiments show that hTPO_(163) interacts with soluble c-MpI containing the extracellular cytokine receptor homology domains with 1:2 stoichiometry with the binding constants of 3.3 x 10~9 M~(-1) and 1.1 x 10~6 M~(-1). The presence of the neutralizing Fab did not inhibit binding of hTPO_(163) to soluble c-MpI fragments, but the lower-affinity binding disappeared. Together with prior genetic data, these define the structure-function relationships in TPO and the activation scheme of c-Mpl.
机译:细胞因子血小板生成素(TPO)是造血受体c-MpI的配体,是巨核细胞-造血功能和血小板生成的主要调节剂。我们已经确定了人类TPO(hTPO_(163))的受体结合域的晶体结构,通过与中和Fab片段复合可以达到2.5-A的分辨率。 hTPO_(163)的骨架结构具有反平行的四螺旋束折叠。中和Fab主要识别包含物种不变残基Q111的C-D交叉环。滴定量热实验表明,hTPO_(163)与含有胞外细胞因子受体同源结构域且化学计量比为1:2的可溶性c-MpI相互作用,结合常数为3.3 x 10〜9 M〜(-1)和1.1 x 10〜6 M 〜(-1)。中和Fab的存在没有抑制hTPO_(163)与可溶性c-MpI片段的结合,但是较低亲和力的结合消失了。这些与先前的遗传数据一起,定义了TPO中的结构-功能关系以及c-Mpl的激活方案。

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