Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.
Nat Commun. 2024 Nov 25;15(1):10198. doi: 10.1038/s41467-024-54575-6.
The proper folding of multispanning membrane proteins (MPs) hinges on the accurate insertion of their transmembrane helices (TMs) into the membrane. Predominantly, TMs are inserted during protein translation, via a conserved mechanism centered around the Sec translocon. Our study reveals that the C-terminal TMs (cTMs) of numerous MPs across various organisms bypass this cotranslational route, necessitating an alternative posttranslational insertion strategy. We demonstrate that evolution has refined the hydrophilicity and length of the C-terminal tails of these proteins to optimize cTM insertion. Alterations in the C-tail sequence disrupt cTM insertion in both E. coli and human, leading to protein defects, loss of function, and genetic diseases. In E. coli, we identify YidC, a member of the widespread Oxa1 family, as the insertase facilitating cTMs insertion, with C-tail mutations disrupting the productive interaction of cTMs with YidC. Thus, MP sequences are fine-tuned for effective collaboration with the cellular biogenesis machinery, ensuring proper membrane protein folding.
多种跨膜蛋白（MPs）的正确折叠依赖于其跨膜螺旋（TMs）准确插入膜中。主要情况下，TMs 是在蛋白质翻译过程中通过围绕 Sec 易位子的保守机制插入的。我们的研究表明，来自各种生物体的众多 MPs 的 C 端 TMs（cTMs）绕过了这种共翻译途径，需要一种替代的翻译后插入策略。我们证明，进化已经优化了这些蛋白质 C 端尾部的亲水性和长度，以优化 cTM 插入。C 端序列的改变会破坏大肠杆菌和人类中的 cTM 插入，导致蛋白质缺陷、功能丧失和遗传疾病。在大肠杆菌中，我们鉴定出 YidC，一种广泛存在的 Oxa1 家族成员，是促进 cTM 插入的插入酶，C 端突变破坏了 cTM 与 YidC 的有效相互作用。因此，MP 序列经过微调，以与细胞生物发生机制有效协作，确保膜蛋白的正确折叠。
