Laboratory of Molecular Biochemistry, CSIR-Institute of Microbial Technology, Chandigarh, India.
Department of Biochemistry, Bose Institute, Kolkata, India.
J Bacteriol. 2014 Jul;196(14):2587-97. doi: 10.1128/JB.01717-14. Epub 2014 May 2.
Manganese is a micronutrient required for activities of several important enzymes under conditions of oxidative stress and iron starvation. In Escherichia coli, the manganese homeostasis network primarily constitutes a manganese importer (MntH) and an exporter (MntP), which are regulated by the MntR dual regulator. In this study, we find that deletion of E. coli hflX, which encodes a ribosome-associated GTPase with unknown function, renders extreme manganese sensitivity characterized by arrested cell growth, filamentation, lower rate of replication, and DNA damage. We demonstrate that perturbation by manganese induces unprecedented influx of manganese in ΔhflX cells compared to that in the wild-type E. coli strain. Interestingly, our study indicates that the imbalance in manganese homeostasis in the ΔhflX strain is independent of the MntR regulon. Moreover, the influx of manganese leads to a simultaneous influx of zinc and inhibition of iron import in ΔhflX cells. In order to review a possible link of HflX with the λ phage life cycle, we performed a lysis-lysogeny assay to show that the Mn-perturbed ΔhflX strain reduces the frequency of lysogenization of the phage. This observation raises the possibility that the induced zinc influx in the manganese-perturbed ΔhflX strain stimulates the activity of the zinc-metalloprotease HflB, the key determinant of the lysis-lysogeny switch. Finally, we propose that manganese-mediated autophosphorylation of HflX plays a central role in manganese, zinc, and iron homeostasis in E. coli cells.
锰是几种重要酶在氧化应激和铁饥饿条件下活性所必需的微量元素。在大肠杆菌中，锰稳态网络主要由锰转运蛋白（MntH）和外排蛋白（MntP）构成，它们受 MntR 双调控因子调控。在这项研究中，我们发现缺失编码未知功能的核糖体相关 GTPase 的 hflX 基因使大肠杆菌对锰极其敏感，表现为细胞生长停滞、丝状化、复制率降低和 DNA 损伤。我们证明，与野生型大肠杆菌菌株相比，锰的扰动诱导了ΔhflX 细胞中前所未有的锰内流。有趣的是，我们的研究表明，ΔhflX 菌株中锰稳态失衡与 MntR 调控子无关。此外，锰的流入导致锌的同时流入和铁的摄取抑制ΔhflX 细胞。为了回顾 HflX 与 λ 噬菌体生命周期之间可能的联系，我们进行了裂解-溶原测定，结果表明 Mn 扰乱的ΔhflX 菌株降低了噬菌体的溶原化频率。这一观察结果提出了一种可能性，即锰扰乱的ΔhflX 菌株中诱导的锌流入刺激了锌金属蛋白酶 HflB 的活性，这是裂解-溶原开关的关键决定因素。最后，我们提出锰介导的 HflX 自动磷酸化在大肠杆菌细胞的锰、锌和铁稳态中起着核心作用。
