Cryo-EM structures of perforin-2 in isolation and assembled on a membrane suggest a mechanism for pore formation.
Cryo-EM structures of perforin-2 in isolation and assembled on a membrane suggest a mechanism for pore formation.
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DOI：
10.15252/embj.2022111857
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发表时间：
2022-12-01
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--
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穿孔蛋白-2（PFN 2，MPEG 1）是哺乳动物先天免疫中限制细胞内细菌增殖的关键成孔蛋白。它形成膜结合的预孔复合物，在酸化时转化为成孔结构;但其构象转变机制一直存在争议。在这里，我们使用冷冻电子显微镜、断层扫描和亚断层图像平均来确定PFN 2在分离和与脂质体结合的前孔和孔构象中的结构。在分离和酸化时，预组装的完整预孔环转化为平环和扭曲构象的孔。在膜上，原位组装的PFN 2前孔显示出不同程度的完整性;而PFN 2孔主要是不完整的弧形结构，其遵循与在隔离中发现的相同的亚基堆积排列。膜上的两种组装体都使用它们的P2 β-发夹结合到脂质膜表面。总的来说，这些结构快照表明PFN 2在靶向膜上的前孔到孔转变的分子机制，可能使用扭曲孔作为平坦构象的中间或替代状态，具有在膜插入期间引起双层扭曲的能力。杀菌性先天免疫蛋白穿孔素-2的Cryo-EM成像揭示了一个大的旋转构象变化，使得在孔形成期间能够插入膜。
Perforin‐2 (PFN2, MPEG1) is a key pore‐forming protein in mammalian innate immunity restricting intracellular bacteria proliferation. It forms a membrane‐bound pre‐pore complex that converts to a pore‐forming structure upon acidification; but its mechanism of conformational transition has been debated. Here we used cryo‐electron microscopy, tomography and subtomogram averaging to determine structures of PFN2 in pre‐pore and pore conformations in isolation and bound to liposomes. In isolation and upon acidification, the pre‐assembled complete pre‐pore rings convert to pores in both flat ring and twisted conformations. On membranes, in situ assembled PFN2 pre‐pores display various degrees of completeness; whereas PFN2 pores are mainly incomplete arc structures that follow the same subunit packing arrangements as found in isolation. Both assemblies on membranes use their P2 β‐hairpin for binding to the lipid membrane surface. Overall, these structural snapshots suggest a molecular mechanism for PFN2 pre‐pore to pore transition on a targeted membrane, potentially using the twisted pore as an intermediate or alternative state to the flat conformation, with the capacity to cause bilayer distortion during membrane insertion. Cryo‐EM imaging of the bactericidal innate immunity protein perforin‐2 reveals a large rotational conformational change that enables membrane insertion during pore formation.
影响因子：
7.3
作者：
Merselis LC;Jiang SY;Nelson SF;Lee H;Prabaker KK;Baker JL;Munson GP;Butte MJ
通讯作者：
Butte MJ