Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
Nat Struct Mol Biol. 2015 Nov;22(11):906-13. doi: 10.1038/nsmb.3103. Epub 2015 Oct 12.
Adverse cellular conditions often lead to nonproductive translational stalling and arrest of ribosomes on mRNAs. Here, we used fast kinetics and cryo-EM to characterize Escherichia coli HflX, a GTPase with unknown function. Our data reveal that HflX is a heat shock-induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes with deacylated tRNA in the peptidyl site. Structural data demonstrate that the N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock. These results suggest a primary role of HflX in rescuing translationally arrested ribosomes under stress conditions.
不良细胞条件通常导致非生产性翻译停滞和核糖体在 mRNA 上的捕获。在这里，我们使用快速动力学和 cryo-EM 来表征具有未知功能的大肠杆菌 HflX，一种 GTPase。我们的数据表明，HflX 是一种热休克诱导的核糖体分裂因子，能够在脱酰基 tRNA 存在的情况下，将空核糖体和与 mRNA 结合的核糖体从肽基转移酶中心解离。结构数据表明，HflX 的 N 端效应结构域以与 I 类释放因子非常相似的方式结合到肽基转移酶中心，并在中央亚基间桥中引起剧烈的构象变化，从而促进亚基解离。因此，HflX 的缺失会导致热休克时核糖体停滞增加。这些结果表明 HflX 在应激条件下拯救翻译失活的核糖体中发挥主要作用。
