MECHANISMS OF ANTIGEN ANTIBODY INTERACTIONS

前些年的研究表明，高亲和力的抗酵母iso-1 细胞色素c单抗(MAb)2-96-12和4-74-6 相关表位。然而，尽管4-74-6的特异性很强 严格的2-96-12杂交与许多进化上有亲缘关系的CYT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2-96-12、4-74-6和 另设抗iso-1单抗4-128-6为对照。一个FV片段包括 轻链和重链的可变区V-L和V-H， 分别为免疫球蛋白。先前确定的cdna序列 用来推导氨基酸序列。例外情况是8 V-H和V-L的氨基末端残基没有测定到4-74-6 和2-96-12的V-L的4-128-6和8个氨基末端残基 从信使核糖核酸序列中推断出来。研究结果表明： 氨基酸在结合部位的呈现是明显的 在2-96-12和4-74-6中不同，特别是在芳香族方面 残留物。2-96-12中的Arg 95H和4-74-6中的Arg 91L 将它们的侧链投射到结合的中心区域 场地或其附近。这些侧链位置由 抗体Fab片段已知结构的比较研究。一个 前几年的Arg 95 H的替代试验也是兼容的 和模特在一起。FV与抗原对接的表位分析 还进行了模特表演。以前的免疫学研究和现在 对接的结果加在一起，符合这样的想法 ISO-1 Asp 60和Glu 61将定位在靠近Arg 95 H的位置 2-96-12与精氨酸91中的L在4-74-6中形成抗原抗体复合体。 因此，我们提出，在严格程度上的明显差异 2-96-12和4-74-6之间的抗原识别可能与 氨基酸在结合部位的呈现方式截然不同 尽管表位相似。

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.