Flomenberg P, Gutierrez E, Hogan K T
Department of Medicine, Medical College of Wisconsin, Milwaukee.
Mol Immunol. 1994 Nov;31(16):1277-84. doi: 10.1016/0161-5890(94)90078-7.
The adenovirus early region 3 glycoprotein E3-19k binds to and inhibits expression of class I major histocompatibility complex (MHC)-encoded molecules, which may help infected cells evade immune recognition. The role of specific regions of the class I MHC molecule in the interaction with E3-19k was evaluated using a series of HLA-A2.1-, HLA-A2 variant-, and HLA-B7-expressing cell lines. The monoclonal antibody (mAb) W6/32, which recognizes a monomorphic epitope on class I MHC molecules, readily co-immunoprecipitated E3-19k with HLA-A2.1 and 14 different HLA-A2 variant molecules that differ from HLA-A2.1 by single amino acid substitutions. Thus, no single residue tested in the regions of the class I MHC molecule that bind peptide or the T-cell receptor controls the binding to E3-19k. Additional immunoprecipitations performed with mAbs directed against well-defined epitopes on the surface of HLA-A2.1 revealed a dichotomy in the ability of the mAbs to co-immunoprecipitate HLA-A2.1 and E3-19k. The mAbs LGIII-220 (directed against the C-terminal end of the alpha 1-helix), CR11-351 (directed against the N-terminal end of the alpha 2-helix), and PA2.1 (directed against the middle of the alpha 2-helix and an underlying beta-loop) readily co-precipitated HLA-A2.1 and E3-19k. In contrast, mAbs MA2.1 (directed against the N-terminal end of the alpha 1-helix and the C-terminal end of the alpha 2-helix) and HO-2 (directed against the N-terminal end of the alpha 1-helix) did not co-precipitate E3-19k with HLA-A2.1. Similarly, mAb MB40.2 (directed against residues 169-182 of HLA-B7) also did not co-precipitate E3-19k with HLA-B7. These studies lead to the conclusion that the N-terminal end of the alpha 1-helix and the C-terminal end of the alpha 2-helix play an important role in dictating the ability of the E3-19k protein to bind to the class I MHC molecule.
腺病毒早期区域3糖蛋白E3-19k与I类主要组织相容性复合体（MHC）编码的分子结合并抑制其表达，这可能有助于受感染细胞逃避免疫识别。使用一系列表达HLA-A2.1、HLA-A2变体和HLA-B7的细胞系评估了I类MHC分子特定区域在与E3-19k相互作用中的作用。识别I类MHC分子上一个单态表位的单克隆抗体（mAb）W6/32很容易与HLA-A2.1以及14种不同的HLA-A2变体分子共免疫沉淀E3-19k，这些变体分子与HLA-A2.1在单个氨基酸取代上存在差异。因此，在I类MHC分子中结合肽或T细胞受体的区域中测试的任何单个残基都不控制与E3-19k的结合。用针对HLA-A2.1表面明确表位的mAb进行的额外免疫沉淀显示，这些mAb在共免疫沉淀HLA-A2.1和E3-19k的能力上存在二分法。mAb LGIII-220（针对α1螺旋的C末端）、CR11-351（针对α2螺旋的N末端）和PA2.1（针对α2螺旋中部和一个潜在的β环）很容易共沉淀HLA-A2.1和E3-19k。相反，mAb MA2.1（针对α1螺旋的N末端和α2螺旋的C末端）和HO-2（针对α1螺旋的N末端）不与HLA-A2.1共沉淀E3-19k。同样，mAb MB40.2（针对HLA-B7的169-182位残基）也不与HLA-B7共沉淀E3-19k。这些研究得出结论，α1螺旋的N末端和α2螺旋的C末端在决定E3-19k蛋白与I类MHC分子结合的能力方面起着重要作用。
