Gherardi Ermanno, Sandin Sara, Petoukhov Maxim V, Finch John, Youles Mark E, Ofverstedt Lars-Göran, Miguel Ricardo N, Blundell Tom L, Vande Woude George F, Skoglund Ulf, Svergun Dmitri I
Medical Research Council Centre and Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
Proc Natl Acad Sci U S A. 2006 Mar 14;103(11):4046-51. doi: 10.1073/pnas.0509040103. Epub 2006 Mar 6.
The polypeptide growth factor, hepatocyte growth factor/scatter factor (HGF/SF), shares the multidomain structure and proteolytic mechanism of activation of plasminogen and other complex serine proteinases. HGF/SF, however, has no enzymatic activity. Instead, it controls the growth, morphogenesis, or migration of epithelial, endothelial, and muscle progenitor cells through the receptor tyrosine kinase MET. Using small-angle x-ray scattering and cryo-electron microscopy, we show that conversion of pro(single-chain)HGF/SF into the active two-chain form is associated with a major structural transition from a compact, closed conformation to an elongated, open one. We also report the structure of a complex between two-chain HGF/SF and the MET ectodomain (MET928) with 1:1 stoichiometry in which the N-terminal and first kringle domain of HGF/SF contact the face of the seven-blade beta-propeller domain of MET harboring the loops connecting the beta-strands b-c and d-a, whereas the C-terminal serine proteinase homology domain binds the opposite "b" face. Finally, we describe a complex with 2:2 stoichiometry between two-chain HGF/SF and a truncated form of the MET ectodomain (MET567), which is assembled around the dimerization interface seen in the crystal structure of the NK1 fragment of HGF/SF and displays the features of a functional, signaling unit. The study shows how the proteolytic mechanism of activation of the complex proteinases has been adapted to cell signaling in vertebrate organisms, offers a description of monomeric and dimeric ligand-receptor complexes, and provides a foundation to the structural basis of HGF/SF-MET signaling.
多肽生长因子肝细胞生长因子/分散因子（HGF/SF）与纤溶酶原及其他复杂丝氨酸蛋白酶具有多结构域结构和蛋白水解激活机制。然而，HGF/SF没有酶活性。相反，它通过受体酪氨酸激酶MET控制上皮细胞、内皮细胞和肌肉祖细胞的生长、形态发生或迁移。利用小角X射线散射和冷冻电子显微镜，我们发现单链前体HGF/SF转化为活性双链形式与从紧密、封闭构象到伸长、开放构象的主要结构转变相关。我们还报道了化学计量比为1:1的双链HGF/SF与MET胞外结构域（MET928）之间复合物的结构，其中HGF/SF的N端和第一个kringle结构域与MET七叶β-螺旋桨结构域中连接β链b-c和d-a的环所在的面接触，而C端丝氨酸蛋白酶同源结构域与相对的“b”面结合。最后，我们描述了双链HGF/SF与MET胞外结构域截短形式（MET567）化学计量比为2:2的复合物，该复合物围绕HGF/SF的NK1片段晶体结构中所见的二聚化界面组装，并显示出功能性信号单元的特征。该研究展示了复杂蛋白酶激活的蛋白水解机制如何适应脊椎动物中的细胞信号传导，描述了单体和二聚体配体-受体复合物，并为HGF/SF-MET信号传导的结构基础提供了依据。
