Till Katharina, Seinen Anne-Bart, Wruck Florian, Sunderlikova Vanda, Galmozzi Carla V, Katranidis Alexandros, Bukau Bernd, Kramer Günter, Tans Sander J
AMOLF, Amsterdam 1098 XG, Netherlands.
Center for Molecular Biology of Heidelberg University (ZMBH), German Cancer Research Center (DKFZ)-ZMBH Alliance, Heidelberg 69120, Germany.
Proc Natl Acad Sci U S A. 2025 Jul 29;122(30):e2422678122. doi: 10.1073/pnas.2422678122. Epub 2025 Jul 25.
Conformational control of nascent chains is poorly understood. Chaperones are known to stabilize, unfold, and disaggregate polypeptides away from the ribosome. In comparison, much less is known about the elementary conformational control mechanisms at the ribosome. Yet, proteins encounter major folding and aggregation challenges during translation. Here, using selective ribosome profiling and optical tweezers with correlated single-molecule fluorescence, with dihydrofolate reductase (DHFR) as a model system, we show that the chaperone trigger factor (TF) accelerates nascent chain folding. TF scans nascent chains by transient binding events, and then locks into a stable binding mode as the chain collapses and folds. This interplay is reciprocal: TF binding collapses nascent chains and stabilizes partial folds, while nascent chain compaction prolongs TF binding. Ongoing translation controls these cooperative effects, with TF-accelerated folding depending on the emergence of a peptide segment that is central to the core DHFR beta-sheet. The folding acceleration we report here impacts processes that depend on folding occurring cotranslationally, including cotranslational protein assembly, protein aggregation, and translational pausing, and may be relevant to other domains of life.
新生肽链的构象控制目前还知之甚少。已知伴侣蛋白可使多肽在核糖体之外保持稳定、展开并解聚。相比之下，对于核糖体上的基本构象控制机制则了解得少得多。然而，蛋白质在翻译过程中会遇到主要的折叠和聚集挑战。在此，我们以二氢叶酸还原酶（DHFR）作为模型系统，利用选择性核糖体分析和带有相关单分子荧光的光镊技术，表明伴侣蛋白触发因子（TF）可加速新生肽链的折叠。TF通过瞬时结合事件扫描新生肽链，然后随着肽链折叠塌陷而锁定为稳定的结合模式。这种相互作用是相互的：TF结合使新生肽链折叠塌陷并稳定部分折叠结构，而新生肽链的压缩则延长TF的结合时间。正在进行的翻译控制着这些协同效应，TF加速的折叠取决于核心DHFRβ折叠的核心肽段的出现。我们在此报道的折叠加速影响了依赖于共翻译折叠的过程，包括共翻译蛋白质组装、蛋白质聚集和翻译暂停，并且可能与生命的其他领域相关。
