Proline cis-trans conformational isomerization is a mechanism that affects different types of protein functions and behaviors. Using analytical characterization, structural analysis, and molecular dynamics simulations, we studied the causes of an aberrant two-peak size-exclusion chromatography profile observed for a trispecific anti-HIV antibody. We found that proline isomerization in the tyrosine-proline-proline (YPP) motif in the heavy chain complementarity-determining region (CDR)3 domain of one of the antibody arms (10e8v4) was a component of this profile. The pH effect on the conformational equilibrium that led to these two populations was presumably caused by a histidine residue (H147) in the light chain that is in direct contact with the YPP motif. Finally, we demonstrated that, due to chemical equilibrium between the cis and trans proline conformers, the antigen-binding potency of the trispecific anti-HIV antibody was not significantly affected in spite of a potential structural clash of 10e8v4 YPtransPtrans conformers with the membrane-proximal ectodomain region epitope in the GP41 antigen. Altogether, these results reveal at mechanistic and molecular levels the effect of proline isomerization in the CDR on the antibody binding and analytical profiles, and support further development of the trispecific anti-HIV antibody.

中文翻译：

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脯氨酸异构化对抗原结合的影响和三特异性抗 HIV 抗体的分析概况。

脯氨酸顺反构象异构化是一种影响不同类型蛋白质功能和行为的机制。我们使用分析表征、结构分析和分子动力学模拟，研究了针对三特异性抗 HIV 抗体观察到的异常双峰大小排阻色谱图的原因。我们发现其中一个抗体臂 (10e8v4) 的重链互补决定区 (CDR)3 结构域中酪氨酸-脯氨酸-脯氨酸 (YPP) 基序中的脯氨酸异构化是该谱的一个组成部分。pH 值对导致这两个群体的构象平衡的影响可能是由与 YPP 基序直接接触的轻链中的组氨酸残基 (H147) 引起的。最后，我们证明了，由于顺式和反式脯氨酸构象异构体之间的化学平衡，尽管 10e8v4 YPtransPtrans 构象异构体与 GP41 中的近膜胞外域区域表位存在潜在的结构冲突，但三特异性抗 HIV 抗体的抗原结合效力并未受到显着影响抗原。总之，这些结果在机械和分子水平上揭示了 CDR 中脯氨酸异构化对抗体结合和分析特征的影响，并支持进一步开发三特异性抗 HIV 抗体。