The rules for the conserved reaction of alphabeta T cell receptors (TCRs) with major histocompatibility complex (MHC) proteins plus peptides are poorly understood, probably because thymocytes bearing TCRs with the strongest MHC reactivity are lost by negative selection. Thus, only TCRs with an attenuated ability to react with MHC appear on mature T cells. Also, the interaction sites between TCRs and MHC may be inherently flexible and hence difficult to spot. We reevaluated contacts between TCRs and MHC in the solved structures of their complexes with these points in mind. Relatively conserved amino acids in the TCR complementarity-determining regions (CDR) 1 and CDR2 are often used to bind exposed areas of the MHC alpha-helices. These areas are exposed because of small amino acids that allow somewhat flexible binding of the TCRs. The TCR amino acids involved are specific to families of variable (V) regions and to some extent different rules may govern the recognition of MHCI versus MHCII.

中文翻译：

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控制 TCR-MHC 相互作用的进化上保守的氨基酸。

对字母 T 细胞受体 (TCR) 与主要组织相容性复合物 (MHC) 蛋白加肽的保守反应规则知之甚少，可能是因为负选择会丢失携带具有最强 MHC 反应性的 TCR 的胸腺细胞。因此，只有与 MHC 反应能力减弱的 TCR 才会出现在成熟 T 细胞上。此外，TCR 和 MHC 之间的相互作用位点可能天生灵活，因此难以发现。我们重新评估了 TCR 和 MHC 在其配合物的已解决结构中的接触，并牢记这些要点。TCR 互补决定区 (CDR) 1 和 CDR2 中相对保守的氨基酸通常用于结合 MHC α-螺旋的暴露区域。这些区域由于允许 TCR 灵活结合的小氨基酸而暴露。