Lowen Sarah M, Waudby Christopher A, Jagger Alistair M, Aldobiyan Ibrahim, Laffranchi Mattia, Fra Annamaria, Christodoulou John, Irving James A, Lomas David A
UCL Respiratory, Rayne Institute, and the Institute of Structural and Molecular Biology, University College London, London WC1E 6JF, UK.
UCL School of Pharmacy, University College London, London WC1N 1AX, UK.
Sci Adv. 2025 May 9;11(19):eadu7064. doi: 10.1126/sciadv.adu7064. Epub 2025 May 7.
Serpins, protease inhibitors whose regulated conformational instability renders them susceptible to mutations that cause misfolding, represent a system for the study of non-amyloid protein aggregation. The E342K "Z" variant of α-1-antitrypsin (AAT) undergoes oligomeric self-assembly into polymer chains that are associated with liver and lung pathologies in AAT deficiency. Structural characterization of polymers from human tissue has been limited by their heterogeneity and flexibility; here, we have studied their internal structure, which provides insights into the molecular linkage and the pathway by which they are formed. NMR spectra of heat-induced C-ILV-methyl-labeled polymers, and H-methyl spectra of liver-derived polymers, show equivalence to that of AAT in a post-protease-encounter conformation. This is corroborated by x-ray crystallography, which reveals a cryptic epitope recognized by the conformationally selective 2C1 antibody, common to both forms. These data definitively preclude most models of polymerization and are compatible with sequential intermolecular donation of the carboxyl terminus of one molecule into the next during polymer formation.
丝氨酸蛋白酶抑制剂（Serpins）是一类蛋白酶抑制剂，其受调控的构象不稳定性使其易受导致错误折叠的突变影响，代表了一个用于研究非淀粉样蛋白聚集的系统。α-1-抗胰蛋白酶（AAT）的E342K “Z” 变体经历寡聚体自组装形成聚合物链，这些聚合物链与AAT缺乏症中的肝脏和肺部病变相关。来自人体组织的聚合物的结构表征受到其异质性和灵活性的限制；在这里，我们研究了它们的内部结构，这为它们的分子连接以及形成途径提供了见解。热诱导的C-异亮氨酸-甲基标记聚合物的核磁共振谱以及肝脏来源聚合物的H-甲基谱显示，在蛋白酶作用后的构象中与AAT的谱相当。X射线晶体学证实了这一点，其揭示了构象选择性2C1抗体识别的一个隐蔽表位，两种形式共有。这些数据明确排除了大多数聚合模型，并且与聚合物形成过程中一个分子的羧基末端依次分子间捐赠给下一个分子的情况相符。
