Colbert R A, Rowland-Jones S L, McMichael A J, Frelinger J A
Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599.
Proc Natl Acad Sci U S A. 1993 Jul 15;90(14):6879-83. doi: 10.1073/pnas.90.14.6879.
To investigate the role of an anchoring pocket in allele-specific peptide presentation by a major histocompatibility complex class I molecule, we "transplanted" a B pocket from HLA-A0201 into HLA-B2705 by site-directed mutagenesis. The resulting protein, designated B27.A2B, binds a different set of endogenous peptides than B2705 as evidenced by complete loss of allorecognition as well as restored expression in the antigen processing-defective mutant cell line T2. B27.A2B also fails to present an HLA-B27-restricted influenza virus peptide [nucleoprotein (383-391)] to cytotoxic T lymphocytes (CTLs). However, substitution of leucine, the predominant P2 anchor residue in A0201-restricted peptides, for arginine, the P2 anchor in nucleoprotein-(383-391) and other B2705-restricted peptides, restores recognition of B27.A2B by the same B2705-restricted peptide-specific CTLs. These results demonstrate that a dominant polymorphic pocket in a class I molecule, through interaction with the anchor residue of an antigenic peptide, can distinguish among peptides differing by only a single amino acid and thus determine the allelic specificity of peptide presentation.
为了研究锚定口袋在主要组织相容性复合体 I 类分子的等位基因特异性肽提呈中的作用，我们通过定点诱变将 HLA-A0201 的 B 口袋“移植”到 HLA-B2705 中。所得蛋白质命名为 B27.A2B，与 B2705 结合的内源性肽组不同，这一点通过同种异体识别的完全丧失以及在抗原加工缺陷型突变细胞系 T2 中的恢复表达得以证明。B27.A2B 也无法将 HLA-B27 限制性流感病毒肽[核蛋白(383 - 391)]提呈给细胞毒性 T 淋巴细胞(CTL)。然而，将 A0201 限制性肽中主要的 P2 锚定残基亮氨酸替换为核蛋白-(383 - 391)和其他 B2705 限制性肽中的 P2 锚定残基精氨酸，可恢复相同的 B2705 限制性肽特异性 CTL 对 B27.A2B 的识别。这些结果表明，I 类分子中的一个显性多态口袋通过与抗原肽的锚定残基相互作用，可以区分仅相差一个氨基酸的肽，从而决定肽提呈的等位基因特异性。
