Ornithine capture by a translating ribosome controls bacterial polyamine synthesis
Ornithine capture by a translating ribosome controls bacterial polyamine synthesis
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DOI：
10.1038/s41564-020-0669-1
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发表时间：
2020-02-24
影响因子：
28.3
通讯作者：
Innis, C. Axel
中科院分区：
文献类型：
--
作者：
Herrero del Valle, Alba;Seip, Britta;Innis, C. Axel
多胺是必需的代谢物，在细胞生长、应激适应和微生物毒力中发挥重要作用(1-3)。为了在人类宿主内生存和繁殖，病原菌会根据不同的环境压力和代谢线索调整多胺生物合成酶的表达和活性(2)。在这里，我们表明，核糖体和新生肽 SpeFL 捕获鸟氨酸，通过涉及核糖体停滞和转录抗终止的机制诱导鸟氨酸脱羧酶 SpeF（4）的表达，控制γ-变形菌中的多胺合成。此外，我们还展示了在鸟氨酸存在的情况下 speFL 翻译过程中停滞的大肠杆菌核糖体的低温电子显微镜结构。该结构显示了核糖体和 SpeFL 传感器结构域如何形成高度选择性的结合袋，该结合袋可容纳单个鸟氨酸分子，但排除近同源配体。鸟氨酸与核糖体预结合，然后被传感器结构域固定到位，导致 SpeFL 效应结构域压缩并阻断释放因子 1 的作用。因此，我们的研究不仅揭示了新生肽协助核糖体检测特定代谢物的基本策略，而且还提供了评估鸟氨酸如何促进几种人类病原体毒力的框架。 细胞、分子和结构生物学方法解释了翻译核糖体和新生肽SpeFL如何相互作用形成结合袋，该结合袋充当鸟氨酸传感器来调节病原菌中的多胺生物合成。
Polyamines are essential metabolites that play an important role in cell growth, stress adaptation and microbial virulence(1-3). To survive and multiply within a human host, pathogenic bacteria adjust the expression and activity of polyamine biosynthetic enzymes in response to different environmental stresses and metabolic cues(2). Here, we show that ornithine capture by the ribosome and the nascent peptide SpeFL controls polyamine synthesis in gamma-proteobacteria by inducing the expression of the ornithine decarboxylase SpeF(4), via a mechanism involving ribosome stalling and transcription antitermination. In addition, we present the cryogenic electron microscopy structure of an Escherichia coli ribosome stalled during translation of speFL in the presence of ornithine. The structure shows how the ribosome and the SpeFL sensor domain form a highly selective binding pocket that accommodates a single ornithine molecule but excludes near-cognate ligands. Ornithine pre-associates with the ribosome and is then held in place by the sensor domain, leading to the compaction of the SpeFL effector domain and blocking the action of release factor 1. Thus, our study not only reveals basic strategies by which nascent peptides assist the ribosome in detecting a specific metabolite, but also provides a framework for assessing how ornithine promotes virulence in several human pathogens.A combination of cellular, molecular and structural biology approaches explains how the translating ribosome and the nascent peptide SpeFL interact to form a binding pocket that serves as an ornithine sensor to regulate polyamine biosynthesis in pathogenic bacteria.