Co-translational assembly counteracts promiscuous interactions

During the co-translational assembly of protein complexes, a fully synthesized subunit engages with the nascent chain of a newly synthesized interaction partner. Such events are thought to contribute to productive assembly, but their exact physiological relevance remains underexplored. Here, we examined structural motifs contained in nucleoporins for their potential to facilitate co-translational assembly. We experimentally tested candidate structural motifs and identified several previously unknown co-translational interactions. We demonstrate by selective ribosome profiling that domain invasion motifs of beta-propellers, coiled-coils, and short linear motifs act as co-translational assembly domains. Such motifs are often contained in proteins that are members of multiple complexes (moonlighters) and engage with closely related paralogs. Surprisingly, moonlighters and paralogs assembled co-translationally in only one but not all of the relevant assembly pathways. Our results highlight the regulatory complexity of assembly pathways.

在蛋白质复合物的共翻译组装（co-translational assembly）过程中，一条完全合成的蛋白质亚基会与新合成的互作伴侣的新生肽链（nascent chain）相结合。此类事件被认为有助于高效组装，但其确切的生理相关性仍未得到充分探索。本研究针对核孔蛋白（nucleoporins）所包含的结构模体，检验其促进共翻译组装的潜力。我们通过实验验证了候选结构模体，并鉴定出数种此前未被发现的共翻译互作关系。我们借助选择性核糖体谱（selective ribosome profiling）技术证实，β螺旋桨、卷曲螺旋以及短线性模体的结构入侵模体（domain invasion motifs）可作为共翻译组装结构域发挥功能。此类模体常存在于隶属于多种复合物的兼性多功能蛋白（moonlighters）以及与近缘旁系同源蛋白（paralogs）存在互作的蛋白质中。令人意外的是，兼性多功能蛋白与旁系同源蛋白仅在一条而非全部相关组装通路中发生共翻译组装。本研究结果凸显了蛋白质组装通路的调控复杂性。