计算差异视角下MHC-I与MHC-II的TCR-pMHC结构预测资源概述与测评
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1)上海理工大学健康科学与工程学院,上海 200093;2)复旦大学药学院,上海市疾病与健康基因组学重点实验室,国家卫生健康委员会计划生育药具重点实验室, 上海市生物医药技术研究院,上海 200237;3)四川大学生命科学学院,生物资源与生态环境教育部重点实验室,成都 610065;4)四川大学生命科学学院,四川省动物疫病防控与食品安全重点实验室,四川省微生物与代谢工程重点实验室,成都 610065

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上海市生物医药技术研究院省部级重点实验室创新能力专项(RC2023-01,DT2025-05),上海科学院关键共性技术专项(SKY2022003)和国家自然科学基金(32470696)资助。


A Computational Perspective on Differences Between MHC-I and MHC-II in TCR-pMHC Structure Prediction Resources: Review and Benchmarking
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1)School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China;2)Shanghai-MOST Key Laboratory of Health and Disease Genomics, NHC Key Lab of Reproduction Regulation, Shanghai Institute for Biomedical and Pharmaceutical Technologies, School of Pharmacy, Fudan University, Shanghai 200237, China;3)Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, China;4)Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province, Microbiology and Metabolic Engineering Key Laboratory of Sichuan Province, College of Life Sciences, Sichuan University, Chengdu 610065, China

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This work was supported by grants from the Innovation Promotion Program of NHC and the Shanghai Key Laboratory of SIBPT (RC2023-01, DT2025-05), Shanghai Academy of Science & Technology (SKY2022003), and The National Natural Science Foundation of China (32470696).

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    摘要:

    T细胞受体(T cell receptor,TCR)对肽-主要组织相容性复合物(peptide-major histocompatibility complex,pMHC)的特异性识别,是触发抗原特异性免疫应答的关键分子事件之一。因此,解析TCR-pMHC复合物的结构特征,不仅为阐明抗原特异性免疫识别机制奠定基础,也为疫苗设计、TCR免疫治疗靶点研究,以及TCR鉴定与优化提供重要依据。然而,由于实验测定成本高、周期长且覆盖范围有限,通过计算方法快速获得可靠的TCR-pMHC复合物结构已成为免疫学研究的重要诉求。近年来,随着深度学习的不断发展,加之结构和序列资源日益丰富,涌现出多种TCR-pMHC计算建模工具。但是,多数工具在建模时未对MHC-I类与MHC-II类复合物之间的关键差异加以区分,导致二者的建模效果存在明显差别。这些工具对I类复合物的预测通常优于II类复合物,这一现象可能源于二者在肽结合槽构型、肽段长度范围及肽段侧翼残基(peptide flanking residues,PFRs)特性等方面的不同。此外,TCR识别界面中,互补决定区(complementarity determining regions,CDRs)通常存在构象柔性,不少工具为追求整体构象稳定性或降低结构噪声,往往过度约束了本应具有柔性的区域。这种过度约束可能导致柔性CDRs被不当刚化,从而引发局部结构畸变、界面几何失真,甚至导致复合物建模失败。为此,本综述基于MHC-I和MHC-II的计算差异视角,系统整理并归纳了TCR和pMHC相关资源,包括结构数据库、序列数据库和结构预测工具。随后构建了包含25个I类和10个II类TCR-pMHC复合物数据集,对AlphaFold2、AlphaFold3、TCRmodel2、tFold-TCR及TCR-pHLA_ModellerS五种能同时预测I类和II类复合物的代表性工具开展系统评估。通过计算全原子RMSD(All-Atom Root Mean Square Deviation,All-Atom RMSD)、主链RMSD(Backbone RMSD)、模板建模得分(Template Modeling score,TM-score)和DockQ,衡量各工具在MHC-I类和MHC-II类复合物整体结构及结合界面建模的准确性。针对MHC-II类复合物,创新性地提出PFR构象偏差指数,包括PFRs-Deviation Index(PFRs-DI)、N-PFR-Deviation Index(N-PFR-DI)与C-PFR-Deviation Index(C-PFR-DI),以评估PFRs的构象准确性。同时,提出CDR构象一致性指数(CDR conformational consistency,CCC),定性评估预测工具刻画TCR CDRs构象柔性的能力。上述指标共同用于评价工具在整体构象与关键区域的建模能力,在一定程度上弥补了通用蛋白质结构模型评测指标偏重整体构象,难以准确反映关键功能区域建模质量的不足,从而构建适用于MHC-I类与MHC-II类复合物的分析框架,用于指导数据资源选择、建模策略制定与评价体系构建,进一步推动计算建模的发展,为多尺度解析TCR-pMHC识别机制及其生物学功能提供重要支撑。

    Abstract:

    The initiation of adaptive immune responses relies on the precise recognition and interpretation of antigenic information. In this process, the specific binding of T cell receptors (TCRs) to peptide-major histocompatibility complex (pMHC) molecules represents one of the key molecular events in the initiation of adaptive immune responses. Accordingly, the structural features of TCR-pMHC complexes provide a fundamental basis for dissecting antigen recognition mechanisms and support rational vaccine design, therapeutic target discovery in TCR-based immunotherapy, and TCR identification and optimization. However, experimental determination of TCR-pMHC structures remains costly, time-consuming, and limited in coverage, making computational approaches essential for rapidly obtaining reliable structural information. Computational methods for predicting the structures of TCR-pMHC complexes have advanced rapidly in recent years, driven by progress in deep learning-based modeling frameworks and the increasing availability of structural and sequence resources. Despite these developments, most existing tools do not adequately distinguish the key structural and biophysical differences between MHC class I (MHC-I) and MHC class II (MHC-II) complexes during model construction. As a consequence, their predictive performance differs substantially between class I and class II complexes. In general, structural predictions for class I complexes outperform those for class II complexes. This discrepancy may be related to several fundamental differences between the two systems, including the architecture of the peptide-binding groove, the distribution of peptide lengths, and the properties of peptide flanking residues (PFRs). Compared with MHC-I molecules, MHC-II molecules usually bind longer antigenic peptides, which typically range from 13 to 25 amino acids in length. PFRs at both termini of these peptides participate in regulating the overall conformation of TCR-pMHC class II complexes and exert a pronounced effect on the geometric and physicochemical characteristics of the TCR-pMHC binding interface. Furthermore, within the TCR recognition interface, the complementarity-determining regions (CDRs) consist of segments that differ markedly in conformational behavior. They commonly include regions that are relatively rigid and structurally stable, together with highly flexible segments exhibiting substantial conformational plasticity. These rigidity-flexibility features constitute an essential structural basis enabling TCRs to recognize diverse peptide-MHC ligands and to accommodate conformational heterogeneity at the interface. However, many current modeling tools, in an effort to enforce global conformational stability or reduce structural noise, tend to over-constrain intrinsically flexible regions. Such oversimplification may lead to inappropriate rigidification of flexible CDR loops, resulting in local structural distortions, compromised interface geometry, or even complete modeling failure for specific complexes. Against this background, the review approaches the field from the perspective of computational differences between MHC-I and MHC-II complexes. We first systematically organize and summarize available resources related to TCRs and pMHCs, including structural datasets, sequence databases, prediction tools, and benchmarking studies. We then focus on five representative tools capable of predicting both class I and class II complexes—AlphaFold2, AlphaFold3, TCRmodel2, tFold-TCR, and TCR-pHLA_ModellerS. After excluding structures present in the training sets of these tools, we constructed a benchmark dataset comprising 25 class I and 10 class II TCR-pMHC complexes in the bound state and conducted a systematic evaluation using this dataset. We first employ widely used general evaluation metrics, including All-Atom Root Mean Square Deviation (All-Atom RMSD), Backbone RMSD, Template Modeling score (TM-score), and DockQ, to assess the global conformational accuracy and interface modeling quality of class I and class II complexes. For class II complexes, we propose for the first time a peptide flanking residue deviation index, including the PFRs-Deviation Index (PFRs-DI), N-PFR-Deviation Index (N-PFR-DI), and C-PFR-Deviation Index (C-PFR-DI), to quantitatively characterize conformational deviations in PFRs. In addition, we propose the CDR conformational consistency index (CCC) designed to qualitatively evaluate the ability of prediction tools to capture TCR CDR conformational flexibility. These metrics collectively assess a tool’s ability to model both overall conformation and critical functional regions, thereby addressing the limitations of existing evaluation criteria that overemphasize global structure while inadequately capturing modeling quality in key functional areas. This establishes a unified analytical framework for MHC-I and MHC-II complexes to guide data resource selection, modeling strategy formulation, and evaluation system development. The framework further advances computational modeling and provides crucial support for multi-scale analysis of TCR-pMHC recognition mechanisms and their biological functions.

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吴晓芹,刘大伟,李玢瑜,刘扬,曹洋,戴文韬.计算差异视角下MHC-I与MHC-II的TCR-pMHC结构预测资源概述与测评[J].生物化学与生物物理进展,2026,53(5):1376-1399 WU Xiao-Qin, LIU Da-Wei, LI Bin-Yu, LIU Yang, CAO Yang, DAI Wen-Tao. A Computational Perspective on Differences Between MHC-I and MHC-II in TCR-pMHC Structure Prediction Resources: Review and Benchmarking[J]. Progress in Biochemistry and Biophysics,2026,53(5):1376-1399

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  • 收稿日期:2026-01-09
  • 最后修改日期:2026-05-07
  • 录用日期:2026-04-02
  • 在线发布日期: 2026-04-03
  • 出版日期: 2026-05-28
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