Yuan Cai, Chen Liqing, Meehan Edward J, Daly Norelle, Craik David J, Huang Mingdong, Ngo Jacky C
State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
BMC Struct Biol. 2011 Jun 22;11:30. doi: 10.1186/1472-6807-11-30.
Matriptase is a type II transmembrane serine protease that is found on the surfaces of epithelial cells and certain cancer cells. Matriptase has been implicated in the degradation of certain extracellular matrix components as well as the activation of various cellular proteins and proteases, including hepatocyte growth factor and urokinase. Sunflower trypsin inhibitor-1 (SFTI-1), a cyclic peptide inhibitor originally isolated from sunflower seeds, exhibits potent inhibitory activity toward matriptase.
We have engineered and produced recombinant proteins of the matriptase protease domain, and have determined the crystal structures of the protease:SFTI-1 complex at 2.0 Å as well as the protease:benzamidine complex at 1.2 Å. These structures elaborate the structural basis of substrate selectivity of matriptase, and show that the matriptase S1 substrate specificity pocket is larger enough to allow movement of benzamidine inside the S1 pocket. Our study also reveals that SFTI-1 binds to matriptase in a way similar to its binding to trypsin despite the significantly different isoelectric points of the two proteins (5.6 vs. 8.2).
This work helps to define the structural basis of substrate specificity of matriptase and the interactions between the inhibitor and protease. The complex structure also provides a structural template for designing new SFTI-1 derivatives with better potency and selectivity against matriptase and other proteases.
Matriptase是一种II型跨膜丝氨酸蛋白酶，存在于上皮细胞和某些癌细胞表面。Matriptase与某些细胞外基质成分的降解以及多种细胞蛋白和蛋白酶的激活有关，包括肝细胞生长因子和尿激酶。向日葵胰蛋白酶抑制剂-1（SFTI-1）是一种最初从向日葵种子中分离出的环肽抑制剂，对Matriptase具有强大的抑制活性。
我们构建并生产了Matriptase蛋白酶结构域的重组蛋白，并确定了蛋白酶：SFTI-1复合物在2.0 Å分辨率下的晶体结构以及蛋白酶：苯甲脒复合物在1.2 Å分辨率下的晶体结构。这些结构阐述了Matriptase底物选择性的结构基础，并表明Matriptase的S1底物特异性口袋足够大，允许苯甲脒在S1口袋内移动。我们的研究还表明，尽管两种蛋白质的等电点有显著差异（5.6对8.2），SFTI-1与Matriptase的结合方式与其与胰蛋白酶的结合方式相似。
这项工作有助于确定Matriptase底物特异性的结构基础以及抑制剂与蛋白酶之间的相互作用。该复合物结构还为设计对Matriptase和其他蛋白酶具有更好效力和选择性的新型SFTI-1衍生物提供了结构模板。
