MECHANISMS OF ANTIGEN ANTIBODY INTERACTIONS

前几年的研究表明，高亲和力抗酵母iso-1 细胞色素c单克隆抗体（mAb）2-96-12和4-74-6具有密切的 相关抗原表位 然而，虽然4-74-6的特异性非常高， 严格，2-96-12与许多进化上相关的cyts交叉反应。 C. 为了获得这种现象的分子基础的线索，我们有 对2-96-12、4-74-6和 另一抗-iso-1 mAb 4-128-6作为对照。 Fv片段由以下组成： 轻链和重链的可变结构域V-L和V-H， 免疫球蛋白。 先前确定的cDNA序列 用于推导氨基酸序列。唯一的例外是，8 未测定4-74-6的V-H和V-L氨基端残基 2-96-12的V-L的8个氨基端残基被 从mRNA序列推断。 结果表明： 结合位点的氨基酸呈现明显 在2-96-12和4-74-6中不同，特别是关于芳香族 残基 2-96-12中的Arg 95 H和4-74-6中的Arg 91 L显著 将它们的侧链向结合的中心区域突出， 现场或其附近。 这些侧链位置由 抗体Fab片段的已知结构的比较研究。 一 前几年Arg 95 H的替代试验也是相容的 与模型。 通过抗原与Fv的对接进行表位分析 模型也进行了。 以前的免疫学研究和现在 对接的结果，放在一起，是兼容的想法， iso-1Asp 60和Glu 61的位置接近Arg 95 H， 2-96-12和4-74-6中的Arg 91 L。 因此，我们建议，严格性的明显差异， 2-96-12和4-74-6之间的抗原识别将与 结合位点氨基酸呈现明显不同 尽管在表位上相似。

Studies in previous years have shown that high affinity anti-yeast iso-1 cytochrome c monoclonal antibodies (mAb) 2-96-12 and 4-74-6 have closely related epitopes. However, while the specificity of 4-74-6 is very stringent, 2-96-12 cross reacts with many evolutionarily related cyts. c. To obtain a clue to the molecular basis of this phenomenon, we have carried out molecular modeling of Fv fragments of 2-96-12, 4-74-6 and another anti-iso-1 mAb 4-128-6 as a control. A Fv fragment consist of the variable domains V-L and V-H of the light and heavy chains, respectively of immunoglobins. Previously determined cDNA sequences were used to deduce the amino acid sequences. The exception is that 8 amino-terminal residues of V-H and V-L were not determined for 4-74-6 and 4-128-6 and that 8 amino-terminal residues of V-L of 2-96-12 were deduced from the mRNA sequence. The results show the following: The presentation of amino acids in the combining site is distinctly different in 2-96-12 and 4-74-6, especially with respect to aromatic residues. Arg 95 H in 2-96-12 and Arg 91L in 4-74-6 conspicuously project their side chains toward the central region of the combining site or its vicinity. These side chain positions are supported by comparative studies of known structures of antibody Fab fragments. A substitution test of the Arg 95 H in previous years is also compastible with the model. Epitope analysis by docking of the antigen to the Fv models was also performed. Previous immunological studies and present results of docking, taken together, are compatible with the idea that iso-1 Asp 60 and Glu 61 would be positioned closely to the Arg 95 H in 2-96-12 and the Arg 91 L in 4-74-6 in the antigen -antibody complex. Thus, we propose that the distinct difference in stringency of the antigen recognition between 2-96-12 and 4-74-6 would be related to the distinctly different presentation of amino acids in the combining site despite similarity in the epitopes.