Department of Biochemistry, University of Sherbrooke, Sherbrooke, Quebec, QC, Canada.
Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):15223-8. doi: 10.1073/pnas.1007805107. Epub 2010 Aug 9.
Siderophores are essential factors for iron (Fe) acquisition in bacteria during colonization and infection of eukaryotic hosts, which restrain iron access through iron-binding protein, such as lactoferrin and transferrin. The synthesis of siderophores by Escherichia coli is considered to be fully regulated at the transcriptional level by the Fe-responsive transcriptional repressor Fur. Here we characterized two different pathways that promote the production of the siderophore enterobactin via the action of the small RNA RyhB. First, RyhB is required for normal expression of an important enterobactin biosynthesis polycistron, entCEBAH. Second, RyhB directly represses the translation of cysE, which encodes a serine acetyltransferase that uses serine as a substrate for cysteine biosynthesis. Reduction of CysE activity by RyhB allows serine to be used as building blocks for enterobactin synthesis through the nonribosomal peptide synthesis pathway. Thus, RyhB plays an essential role in siderophore production and may modulate bacterial virulence through optimization of siderophore production.
铁载体对于细菌在真核宿主定植和感染过程中获取铁（Fe）是必不可少的因素，它们通过铁结合蛋白（如乳铁蛋白和转铁蛋白）来限制铁的摄取。大肠杆菌中铁载体的合成被认为是通过 Fe 反应性转录抑制剂 Fur 在转录水平上完全调节的。在这里，我们描述了两条不同的途径，通过小 RNA RyhB 的作用促进了肠杆菌素的产生。首先，RyhB 是正常表达重要肠杆菌素生物合成多顺反子 entCEBAH 所必需的。其次，RyhB 直接抑制编码丝氨酸乙酰基转移酶的 cysE 的翻译，该酶利用丝氨酸作为半胱氨酸生物合成的底物。通过 RyhB 降低 CysE 的活性，丝氨酸可以通过非核糖体肽合成途径被用作肠杆菌素合成的构建块。因此，RyhB 在铁载体的产生中起着至关重要的作用，并可能通过优化铁载体的产生来调节细菌的毒力。
