Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, Madrid, 28049, Spain.
Environ Microbiol. 2018 Oct;20(10):3484-3503. doi: 10.1111/1462-2920.14263. Epub 2018 Aug 5.
Metabolically versatile bacteria use catabolite repression control to select their preferred carbon sources, thus optimizing carbon metabolism. In pseudomonads, this occurs through the combined action of the proteins Hfq and Crc, which form stable tripartite complexes at target mRNAs, inhibiting their translation. The activity of Hfq/Crc is antagonised by small RNAs of the CrcZ family, the amounts of which vary according to carbon availability. The present work examines the role of Pseudomonas putida Hfq protein under conditions of low-level catabolite repression, in which Crc protein would have a minor role since it is sequestered by CrcZ/CrcY. The results suggest that, under these conditions, Hfq remains operative and plays an important role in iron homeostasis. In this scenario, Crc appears to participate indirectly by helping CrcZ/CrcY to control the amount of free Hfq in the cell. Iron homeostasis in pseudomonads relies on regulatory elements such as the Fur protein, the PrrF1-F2 sRNAs, and several extracytoplasmic sigma factors. Our results show that the absence of Hfq is paralleled by a reduction in PrrF1-F2 small RNAs. Hfq thus provides a regulatory link between iron and carbon metabolism, coordinating the iron supply to meet the needs of the enzymes operational under particular nutritional regimes.
具有代谢多功能性的细菌利用分解代谢物阻遏控制来选择其首选的碳源，从而优化碳代谢。在假单胞菌中，这是通过 Hfq 和 Crc 蛋白的共同作用实现的，它们在靶 mRNA 上形成稳定的三联复合物，抑制其翻译。Hfq/Crc 的活性受到 CrcZ 家族小 RNA 的拮抗，其数量根据碳源的可用性而变化。本工作研究了低水平分解代谢物阻遏条件下假单胞菌 Hfq 蛋白的作用，在这种条件下，由于 Crc 蛋白被 CrcZ/CrcY 隔离，其作用较小。结果表明，在这些条件下，Hfq 仍然起作用，并在铁稳态中发挥重要作用。在这种情况下，Crc 似乎通过帮助 CrcZ/CrcY 来控制细胞中游离 Hfq 的数量间接参与。假单胞菌中的铁稳态依赖于调节元件，如 Fur 蛋白、PrrF1-F2 sRNAs 和几个细胞外 sigma 因子。我们的结果表明，Hfq 的缺失伴随着 PrrF1-F2 小 RNA 的减少。因此，Hfq 在铁和碳代谢之间提供了一个调节联系，协调铁的供应以满足特定营养条件下运作的酶的需求。
