Zhang Yuan, Li Ze-Sheng, Sun Miao, Zheng Qing-Chuan, Sun Chia-Chung
Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, PR China.
Biochim Biophys Acta. 2005 Feb 14;1747(1):27-34. doi: 10.1016/j.bbapap.2004.09.022. Epub 2004 Oct 22.
GPX is a mammalian antioxidant selenoenzyme which protects biomembranes and other cellular components from oxidative damage by catalyzing the reduction of a variety of hydroperoxides (ROOH), using Glutathione (GSH) as the reducing substrate. The single-chain Fv fragment of the monoclonal antibody 2F3 (scFv2F3) can be converted into the selenium-containing Se-scFv2F3 by chemical modification of the serine. The new selenium-containing catalytic antibody Se-scFv2F3 acts as a glutathione peroxidase (GPX) mimic with high catalytic efficiency. In order to investigate which residue of scFv2F3 is converted into selenocysteine and to describe the proper reaction site of GSH to Se-scFv2F3, a three-dimensional structure of scFv2F3 is built by means of homology modeling. The 3D model is assessed by molecular dynamics (MD) simulation to determine its stability and by comparison with those of known protein structures. After the serine in the scFv2F3 is modified to selenocysteine, a catalytic antibody (abzyme) is obtained. From geometrical considerations, the solvent-accessible surface of the protein is examined. The computer-aided docking and energy minimization (EM) calculations of the abzyme-GSH complex are then carried out to explore the possible active site of the glutathione peroxidase mimic Se-scFv2F3. The structural information from the theoretically modeled complex can help us to further understand the catalytic mechanism of GPX.
谷胱甘肽过氧化物酶（GPX）是一种哺乳动物抗氧化硒酶，它通过催化多种氢过氧化物（ROOH）的还原反应，以谷胱甘肽（GSH）作为还原底物，保护生物膜和其他细胞成分免受氧化损伤。单克隆抗体2F3的单链Fv片段（scFv2F3）可通过丝氨酸的化学修饰转化为含硒的Se-scFv2F3。新型含硒催化抗体Se-scFv2F3作为谷胱甘肽过氧化物酶（GPX）模拟物，具有高催化效率。为了研究scFv2F3的哪个残基转化为硒代半胱氨酸，并描述GSH与Se-scFv2F3的合适反应位点，通过同源建模构建了scFv2F3的三维结构。通过分子动力学（MD）模拟评估3D模型的稳定性，并与已知蛋白质结构进行比较。将scFv2F3中的丝氨酸修饰为硒代半胱氨酸后，获得一种催化抗体（抗体酶）。从几何角度考虑，检查了蛋白质的溶剂可及表面。然后进行抗体酶-GSH复合物的计算机辅助对接和能量最小化（EM）计算，以探索谷胱甘肽过氧化物酶模拟物Se-scFv2F3的可能活性位点。理论建模复合物的结构信息有助于我们进一步了解GPX的催化机制。
