Trakhanov S, Parkin S, Raffaï R, Milne R, Newhouse Y M, Weisgraber K H, Rupp B
Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, CA 94141, USA.
Acta Crystallogr D Biol Crystallogr. 1999 Jan;55(Pt 1):122-8. doi: 10.1107/S090744499800938X. Epub 1999 Jan 1.
The crystal structure of the Fab fragment of 2E8, the monoclonal IgG1,kappa antibody specific for the low-density lipoprotein (LDL) receptor-binding region of apolipoprotein E (apoE), has been solved by molecular replacement and refined at 1.9 A resolution (PDB entry 12E8). Two 2E8 Fab molecules in the asymmetric unit are related by noncrystallographic symmetry and are hydrogen bonded through a beta-sheet-like intermolecular contact between the heavy-chain complementarity-determining regions 3 (CDRH3) of each molecule. The structure has been refined to an R value of 0.22 (Rfree = 0.27). The initially ill-defined heavy-chain constant domain (CH1) of 2E8 has been retraced with the aid of automatic refinement, confirming the beta-sheet tracing independently of any starting models. As a resolution better than 2 A is not common for Fab fragments, this model represents a well defined Fab structure and should prove useful in MR solution of other Fab fragments. Furthermore, in the absence of an LDL-receptor structure, the homology of the 2E8 CDRH2 to the ligand-binding domain of the LDL receptor has been exploited to model the apoE-LDL-receptor interaction.
2E8是一种针对载脂蛋白E（apoE）低密度脂蛋白（LDL）受体结合区域的单克隆IgG1κ抗体，其Fab片段的晶体结构已通过分子置换法解析，并在1.9埃分辨率下进行了精修（蛋白质数据库条目12E8）。不对称单元中的两个2E8 Fab分子通过非晶体学对称性相关联，并通过每个分子的重链互补决定区3（CDRH3）之间的β折叠样分子间接触形成氢键。该结构已精修至R值为0.22（Rfree = 0.27）。借助自动精修，重新确定了2E8最初定义不明确的重链恒定区（CH1），独立于任何起始模型确认了β折叠轨迹。由于Fab片段分辨率优于2埃并不常见，该模型代表了一个定义明确的Fab结构，应证明对其他Fab片段的分子置换解析有用。此外，在缺乏LDL受体结构的情况下，利用2E8 CDRH2与LDL受体配体结合域的同源性对apoE-LDL受体相互作用进行了建模。
