Banerjee Koyeli, Yakovlev Sergiy, Gruschus James M, Medved Leonid, Tjandra Nico
Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States.
Center for Vascular and Inflammatory Diseases and Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States.
Biochemistry. 2018 Jul 31;57(30):4395-4403. doi: 10.1021/acs.biochem.8b00349. Epub 2018 Jul 17.
Our previous studies revealed that interaction of fibrin with the very low density lipoprotein (VLDL) receptor plays a prominent role in transendothelial migration of leukocytes and thereby inflammation. The major goal of our subsequent studies is to establish the structural basis for this interaction. As the first step toward this goal, we localized the fibrin-binding sites within cysteine-rich (CR) domains 2-4 of the VLDL receptor. In this study, we have made a next step toward this goal by establishing the nuclear magnetic resonance solution structure of the recombinant VLDLR(2-4) fragment containing all three fibrin-binding CR domains of this receptor. The structure revealed that all three CR domains have a similar general fold. Each domain contains a calcium-binding loop, and the loop in the CR3 domain has a unique conformation relative to the other two. Domains CR2 and CR3 interact with each other, while CR4 is flexible relative to the other two domains. In addition, analysis of the electrostatic potential surface of VLDLR(2-4) revealed extended negatively charged regions in each of its CR domains. The presence of these regions suggests that they may interact with three positively charged clusters of the fibrin βN domain whose involvement in interaction with the VLDL receptor was demonstrated earlier. Altogether, these findings provide a solid background for our next step toward establishing the structural basis for fibrin-VLDL receptor interaction.
我们之前的研究表明，纤维蛋白与极低密度脂蛋白（VLDL）受体的相互作用在白细胞的跨内皮迁移以及由此引发的炎症中起着重要作用。我们后续研究的主要目标是确定这种相互作用的结构基础。作为实现这一目标的第一步，我们在VLDL受体富含半胱氨酸（CR）的结构域2 - 4内定位了纤维蛋白结合位点。在本研究中，我们朝着这一目标又迈进了一步，通过确定包含该受体所有三个纤维蛋白结合CR结构域的重组VLDLR(2 - 4)片段的核磁共振溶液结构。该结构表明，所有三个CR结构域具有相似的总体折叠方式。每个结构域都包含一个钙结合环，并且CR3结构域中的环相对于其他两个环具有独特的构象。CR2和CR3结构域相互作用，而CR4相对于其他两个结构域是灵活的。此外，对VLDLR(2 - 4)静电势表面的分析揭示了其每个CR结构域中都有延伸的带负电荷区域。这些区域的存在表明它们可能与纤维蛋白βN结构域的三个带正电荷的簇相互作用，之前已证明这些簇参与与VLDL受体的相互作用。总之，这些发现为我们下一步确定纤维蛋白 - VLDL受体相互作用的结构基础提供了坚实的背景。
