Department of Biochemistry and Microbiology, Rutgers, the State University of New Jersey, New Brunswick, New Jersey, USA.
Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan, USA.
mBio. 2024 Nov 13;15(11):e0231024. doi: 10.1128/mbio.02310-24. Epub 2024 Oct 23.
Iron (Fe) is a trace nutrient required by nearly all organisms. As a result of the demand for Fe and the toxicity of non-chelated cytosolic ionic Fe, regulatory systems have evolved to tightly balance Fe acquisition and usage while limiting overload. In most bacteria, including the mammalian pathogen , the ferric uptake regulator (Fur) is the primary transcriptional regulator controlling the transcription of genes that code for Fe uptake and utilization proteins. Fpa (formerly YlaN) was demonstrated to be essential in unless excess Fe is added to the growth medium, suggesting a role in Fe homeostasis. Here, we demonstrate that Fpa is essential in upon Fe deprivation. Null alleles bypassed the essentiality of Fpa. The absence of Fpa abolished the derepression of Fur-regulated genes during Fe limitation. Bioinformatic analyses suggest that was recruited to Gram-positive bacteria and, once acquired, was maintained in the genome as it co-evolved with Fur. Consistent with a role for Fpa in alleviating Fur-dependent repression, Fpa and Fur interacted , and Fpa decreased the DNA-binding ability of Fur . Fpa bound Fe(II) using oxygen or nitrogen ligands with an association constant that is consistent with a physiological role in Fe homeostasis. These findings have led to a model wherein Fpa is an Fe(II) binding protein that influences Fur-dependent regulation through direct interaction.IMPORTANCEIron (Fe) is an essential nutrient for nearly all organisms. If Fe homeostasis is not maintained, Fe may accumulate in the cytosol, which can be toxic. Questions remain about how cells efficiently balance Fe uptake and usage to prevent overload. Iron uptake and proper metalation of proteins are essential processes in the mammalian bacterial pathogen . Understanding the gene products involved in the genetic regulation of Fe uptake and usage and the physiological adaptations that uses to survive in Fe-depleted conditions provides insight into pathogenesis. Herein, we demonstrate that the DNA-binding activity of the ferric uptake regulator transcriptional repressor is alleviated under Fe limitation, but uniquely, in , alleviation requires the presence of Fpa.
铁（Fe）是几乎所有生物体所需的痕量营养素。由于对 Fe 的需求以及非螯合细胞溶质离子 Fe 的毒性，调节系统已经进化到可以紧密平衡 Fe 的获取和使用，同时限制过载。在大多数细菌中，包括哺乳动物病原体，三价铁摄取调节剂（Fur）是控制编码 Fe 摄取和利用蛋白的基因转录的主要转录调节剂。已经证明 Fpa（以前称为 YlaN）在 中是必需的，除非在生长培养基中添加过量的 Fe，这表明它在 Fe 稳态中起作用。在这里，我们证明在 Fe 剥夺时 中 Fpa 是必需的。缺失的 等位基因绕过了 Fpa 的必需性。在 Fe 限制期间，Fpa 的缺失消除了 Fur 调节基因的去阻遏。生物信息学分析表明， 被招募到革兰氏阳性菌中，一旦获得，就随着 Fur 的共同进化而在基因组中保留下来。与 Fpa 在减轻 Fur 依赖性抑制中的作用一致，Fpa 和 Fur 相互作用，并且 Fpa 降低了 Fur 的 DNA 结合能力。Fpa 使用氧或氮配体结合 Fe(II)，其缔合常数与 Fe 稳态中的生理作用一致。这些发现导致了一种模型，其中 Fpa 是一种 Fe(II)结合蛋白，通过直接相互作用影响 Fur 依赖性调节。
重要性
铁（Fe）是几乎所有生物体的必需营养素。如果不能维持 Fe 稳态，Fe 可能会在细胞质中积累，这可能是有毒的。关于细胞如何有效地平衡 Fe 摄取和利用以防止过载的问题仍然存在。铁摄取和蛋白质的适当金属化是哺乳动物细菌病原体中必不可少的过程。了解参与 Fe 摄取和利用的基因产物以及 用于在 Fe 耗尽条件下生存的生理适应提供了对发病机制的深入了解。在此，我们证明在 Fe 限制下，三价铁摄取调节剂转录抑制剂的 DNA 结合活性得到缓解，但独特的是，在 中，缓解需要 Fpa 的存在。
