Orlandi R, Formantici C, Ménard S, Boyer C M, Wiener J R, Colnaghi M
Istituto Nazionale per lo Studio e la Cura dei Tumori, Division of Experimental Oncology E, Milan, Italy.
Biol Chem. 1997 Nov;378(11):1387-92. doi: 10.1515/bchm.1997.378.11.1387.
Analysis of epitopes recognized by therapeutic monoclonal antibodies (mAb) is critical in clinical applications and in structure/function studies of target antigen. mAb MGr6 recognizes the extracellular domain of the p185HER2 oncoprotein and is a promising candidate for cancer immunodiagnosis and immunotherapy. Thus, epitope location and structure on p185HER2 need to be investigated. The use of MGr6-selected phage-displayed peptides for epitope analysis served to dissect the MGr6 epitope into at least two subregions, mimicked by CHSDC- and (L)P-(L)K(L) phage displayed peptides, respectively. Comparison of amino acid sequences of CHSDC peptides with the p185HER2 protein sequence and analysis of MGr6 reactivity with p185HER2 deletion mutants identified the linear subregion CCHEQCAAG of the MGr6 epitope, corresponding to amino acids 235-243 of the p185HER2 protein. This continuous subregion is part of a larger conformational epitope, and other amino acids, including a proline, a lysine and leucine residues contained in (L)P-(L)K(L) phage-displayed peptides appear to contribute to the formation of the MGr6 epitope surface.
分析治疗性单克隆抗体（mAb）所识别的表位在临床应用以及靶抗原的结构/功能研究中至关重要。单克隆抗体MGr6识别p185HER2癌蛋白的细胞外结构域，是癌症免疫诊断和免疫治疗的一个有前景的候选物。因此，需要研究p185HER2上的表位位置和结构。使用MGr6筛选的噬菌体展示肽进行表位分析，有助于将MGr6表位至少分解为两个亚区域，分别由CHSDC-和（L）P-（L）K（L）噬菌体展示肽模拟。将CHSDC肽的氨基酸序列与p185HER2蛋白序列进行比较，并分析MGr6与p185HER2缺失突变体的反应性，确定了MGr6表位的线性亚区域CCHEQCAAG，对应于p185HER2蛋白的235-243位氨基酸。这个连续的亚区域是一个更大的构象表位的一部分，并且（L）P-（L）K（L）噬菌体展示肽中包含的其他氨基酸，包括一个脯氨酸、一个赖氨酸和亮氨酸残基，似乎有助于MGr6表位表面的形成。
