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Abstract
Ferric uptake regulator (Fur) is a transcriptional regulator that controls the expression of genes involved in the uptake of iron and manganese, as well as vital nutrients, and is essential for intracellular redox cycling. We identified a unique Fur homolog (DR0865) from Deinococcus radiodurans, which is known for its extreme resistance to radiation and oxidants. A dr0865 mutant (Mt-0865) showed a higher sensitivity to manganese stress, hydrogen peroxide, gamma irradiation and ultraviolet (UV) irradiation than the wild-type R1 strain. Cellular manganese (Mn) ion (Mn2+) analysis showed that Mn2+, copper (Cu2+), and ferric (Fe3+) ions accumulated significantly in the mutant, which suggests that the dr0865 gene is not only involved in the regulation of Mn2+ homeostasis, but also affects the uptake of other ions. In addition, transcriptome profiles under MnCl2 stress showed that the expression of many genes involved in Mn metabolism was significantly different in the wild-type R1 and DR0865 mutant (Mt-0865). Furthermore, we found that the dr0865 gene serves as a positive regulator of the manganese efflux pump gene mntE (dr1236), and as a negative regulator of Mn ABC transporter genes, such as dr2283, dr2284 and dr2523. Therefore, it plays an important role in maintaining the homoeostasis of intracellular Mn (II), and also other Mn2+, zinc (Zn2+) and Cu2+ ions. Based on its role in manganese homeostasis, DR0865 likely belongs to the Mur sub-family of Fur homolog.
Highlights
Metal ions, such as manganese (Mn2+) and iron (Fe2+), are essential micronutrients for many microorganisms and act as enzyme cofactors for a wide range of proteins in processes such as DNA synthesis, DNA repair, reactive oxygen species (ROS) scavenging and electron transport [1]
A BLASTP analysis showed that DR0865 exhibits 24% identity to Helicobacter pylori Ferric uptake regulator (Fur) (Hpy-Fur) and 26% identity to the E. coli Fur protein
Further comparison with the Hpy-Fur sequence showed that DR0865 has three similar metal-binding domains
Summary
Metal ions, such as manganese (Mn2+) and iron (Fe2+), are essential micronutrients for many microorganisms and act as enzyme cofactors for a wide range of proteins in processes such as DNA synthesis, DNA repair, reactive oxygen species (ROS) scavenging and electron transport [1]. When in excess, they are toxic to cells. Excess iron induces the over-production of harmful ROS, such as super-oxide anion radicals (O22) and hydrogen peroxide (H2O2) [1]. High levels of ROS may target DNA, RNA, proteins and lipids through the hydroxyl radicals (HON) that are generated from H2O2 in the Fenton reaction, which uses divalent ions [2]. Inhibition of RNA and protein synthesis occur when high intracellular levels of manganese are reached [3]. Microorganisms have evolved efficient mechanisms to maintain metal ion homeostasis [4]
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