Department of Biochemistry and Biomedical Sciences and Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, Ontario, L8N3Z5, Canada.
RNA. 2011 Nov;17(11):2026-38. doi: 10.1261/rna.2922311. Epub 2011 Sep 29.
YjeQ is a protein broadly conserved in bacteria containing an N-terminal oligonucleotide/oligosaccharide fold (OB-fold) domain, a central GTPase domain, and a C-terminal zinc-finger domain. YjeQ binds tightly and stoichiometrically to the 30S subunit, which stimulates its GTPase activity by 160-fold. Despite growing evidence for the involvement of the YjeQ protein in bacterial 30S subunit assembly, the specific function and mechanism of this protein remain unclear. Here, we report the costructure of YjeQ with the 30S subunit obtained by cryo-electron microscopy. The costructure revealed that YjeQ interacts simultaneously with helix 44, the head and the platform of the 30S subunit. This binding location of YjeQ in the 30S subunit suggests a chaperone role in processing of the 3' end of the rRNA as well as in mediating the correct orientation of the main domains of the 30S subunit. In addition, the YjeQ binding site partially overlaps with the interaction site of initiation factors 2 and 3, and upon binding, YjeQ covers three inter-subunit bridges that are important for the association of the 30S and 50S subunits. Hence, our structure suggests that YjeQ may assist in ribosome maturation by preventing premature formation of the translation initiation complex and association with the 50S subunit. Together, these results support a role for YjeQ in the late stages of 30S maturation.
YjeQ 是一种在细菌中广泛保守的蛋白质，包含一个 N 端寡核苷酸/寡糖折叠（OB 折叠）结构域、一个中央 GTPase 结构域和一个 C 端锌指结构域。YjeQ 与 30S 亚基紧密且成比例地结合，从而使其 GTPase 活性增加 160 倍。尽管越来越多的证据表明 YjeQ 蛋白参与细菌 30S 亚基的组装，但该蛋白的具体功能和机制仍不清楚。在这里，我们通过冷冻电子显微镜报告了 YjeQ 与 30S 亚基的共结构。该共结构揭示了 YjeQ 与 30S 亚基的 44 号螺旋、头部和平台同时相互作用。YjeQ 在 30S 亚基中的这种结合位置表明它在 rRNA 3'端加工以及介导 30S 亚基主要结构域的正确取向方面发挥了伴侣的作用。此外，YjeQ 的结合位点部分与起始因子 2 和 3 的相互作用位点重叠，并且在结合时，YjeQ 覆盖了三个对于 30S 和 50S 亚基结合很重要的亚基间桥。因此，我们的结构表明，YjeQ 可能通过防止翻译起始复合物的过早形成和与 50S 亚基的结合来协助核糖体成熟。总之，这些结果支持 YjeQ 在 30S 成熟的后期阶段发挥作用。
