L'Faqihi F E, Praud C, Yassine-Diab B, Enault G, Lakhdar-Ghazal F, de Préval C, Coppin H
INSERM U395, CHU Purpan, Toulouse, France.
Tissue Antigens. 1998 Jan;51(1):10-9. doi: 10.1111/j.1399-0039.1998.tb02942.x.
Two closely-related molecules, DR(alpha,beta10101) and DR(alpha,beta10103), whose beta chains only differ by three amino acids at positions 67, 70, and 71, and six intermediate molecules obtained by site-directed mutagenesis were used to ascertain the respective roles of the three polymorphic residues. Substitutions at positions 70 (D-->Q), 71 (E-->R) and 67 (I or L-->F) strongly affected HA 306-318-specific T-cell recognition. The consequences of the substitution of residue 67 by a phenylalanine depended on the modified HLA-DR molecule. Although this substitution completely inhibited peptide-specific DR1-restricted T-cell recognition, its manifestations on the DR103-restricted T-cell response were variable (abolishing proliferation of some cell lines and not others), no matter what the peptide presented was (HA 306-319 or HIV P25 peptides). We also observed that inhibition of the proliferation of an alloreactive anti-DR103 T-cell clone, caused by a substitution at position 70, was completely cancelled by substitution of residue 67 by a phenylalanine. The observations based on functional experiments, thus, suggest that residue 67 plays an important role in determining conformation of the peptide presented to the T cells. Molecular modeling was used to predict changes induced by amino acid substitutions and highly supports functional data. Substitution of residue 67 by a phenylalanine could have repercussions on the structure of HLA-DR molecule/peptide complexes and affect T-cell recognition.
两个密切相关的分子，DR(α,β10101)和DR(α,β10103)，其β链仅在第67、70和71位的三个氨基酸上有所不同，以及通过定点诱变获得的六个中间分子，被用于确定这三个多态性残基各自的作用。第70位（D→Q）、第71位（E→R）和第67位（I或L→F）的取代强烈影响HA 306 - 318特异性T细胞识别。第67位残基被苯丙氨酸取代的后果取决于修饰后的HLA - DR分子。尽管这种取代完全抑制了肽特异性DR1限制的T细胞识别，但其对DR103限制的T细胞反应的表现是可变的（消除了一些细胞系的增殖而不是其他细胞系），无论呈现的肽是什么（HA 306 - 319或HIV P25肽）。我们还观察到，由第70位取代引起的同种异体反应性抗DR103 T细胞克隆增殖的抑制，被第67位残基被苯丙氨酸取代完全消除。因此，基于功能实验的观察结果表明，第67位残基在决定呈递给T细胞的肽的构象中起重要作用。分子建模用于预测氨基酸取代引起的变化，并高度支持功能数据。第67位残基被苯丙氨酸取代可能会对HLA - DR分子/肽复合物的结构产生影响，并影响T细胞识别。
