Crystal structure of a catalytic antibody with a serine protease active site.
Crystal structure of a catalytic antibody with a serine protease active site.
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DOI：
10.1126/science.8066444
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发表时间：
1994-08
期刊：
影响因子：
56.9
通讯作者：
GW Zhou;Jeffrey Z. Guo;Wei Huang;Robert J. Fletterick;TS Scanlan
中科院分区：
文献类型：
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作者：
GW Zhou;Jeffrey Z. Guo;Wei Huang;Robert J. Fletterick;TS Scanlan
具有结合到活性位点的膦酸酯过渡态类似物（半抗原）的异常活性水解抗体的三维结构已被解决为2.5 A分辨率。抗体（17 E8）催化正亮氨酸和甲硫氨酸苯基酯的水解，并对具有天然α-碳L构型的氨基酸酯具有选择性。抗体催化反应的pH依赖性曲线呈钟形，在pH 9.5时活性最大;机制实验支持共价酰基抗体中间体的形成。结构和动力学数据是互补的，并且支持抗体的水解机制与丝氨酸蛋白酶的水解机制非常相似。抗体活性位点含有接近结合的半抗原的磷原子的Ser-His二联体结构，其类似于丝氨酸蛋白酶的Ser-His-Asp催化三联体的三个组分中的两个。抗体活性位点还含有稳定氧阴离子形成的Lys残基，以及用于正亮氨酸和甲硫氨酸侧链的特异性底物识别的疏水结合口袋。该结构鉴定了介导催化作用的活性位点残基，并提示可能提高抗体催化效率的特定突变。这种催化性抗体-半抗原复合物的高分辨率结构表明，抗体可以聚集在通过天然酶进化产生的活性位点结构上。
The three-dimensional structure of an unusually active hydrolytic antibody with a phosphonate transition state analog (hapten) bound to the active site has been solved to 2.5 A resolution. The antibody (17E8) catalyzes the hydrolysis of norleucine and methionine phenyl esters and is selective for amino acid esters that have the natural alpha-carbon L configuration. A plot of the pH-dependence of the antibody-catalyzed reaction is bell-shaped with an activity maximum at pH 9.5; experiments on mechanism lend support to the formation of a covalent acyl-antibody intermediate. The structural and kinetic data are complementary and support a hydrolytic mechanism for the antibody that is remarkably similar to that of the serine proteases. The antibody active site contains a Ser-His dyad structure proximal to the phosphorous atom of the bound hapten that resembles two of the three components of the Ser-His-Asp catalytic triad of serine proteases. The antibody active site also contains a Lys residue to stabilize oxyanion formation, and a hydrophobic binding pocket for specific substrate recognition of norleucine and methionine side chains. The structure identifies active site residues that mediate catalysis and suggests specific mutations that may improve the catalytic efficiency of the antibody. This high resolution structure of a catalytic antibody-hapten complex shows that antibodies can converge on active site structures that have arisen through natural enzyme evolution.