Abstract
BackgroundDeinococcus radiodurans accumulates high levels of manganese ions, and this is believed to be correlated with the radiation resistance ability of this microorganism. However, the maintenance of manganese ion homeostasis in D. radiodurans remains to be investigated.ResultsIn this study, we identified the manganese efflux protein (MntE) in D. radiodurans. The null mutant of mntE was more sensitive than the wild-type strain to manganese ions, and the growth of the mntE mutant was delayed in manganese-supplemented media. Furthermore, there was a substantial increase in the in vivo concentration of manganese ions. Consistent with these characteristics, the mntE mutant was more resistant to H2O2, ultraviolet rays, and γ-radiation. The intracellular protein oxidation (carbonylation) level of the mutant strain was remarkably lower than that of the wild-type strain.ConclusionsOur results indicated that dr1236 is indeed a mntE homologue and is indispensable for maintaining manganese homeostasis in D. radiodurans. The data also provide additional evidence for the involvement of intracellular manganese ions in the radiation resistance of D. radiodurans.
Highlights
Deinococcus radiodurans accumulates high levels of manganese ions, and this is believed to be correlated with the radiation resistance ability of this microorganism
Our results demonstrated that increased intracellular Mn levels could substantially suppress protein oxidation in D. radiodurans exposed to H2O2, indicating that manganese transport and regulation may be involved in the cellular resistance of D. radiodurans to oxidative stress
D. radiodurans encodes a putative manganese efflux protein By searching the D. radiodurans genome http://www. ncbi.nlm.nih.gov/, we identified a manganese efflux protein homologue that was annotated as the conserved hypothetical protein DR1236 based on its extensive sequence similarity (25% identity, 49% similarity) to the manganese efflux protein of Streptococcus pneumoniae [10]
Summary
Deinococcus radiodurans accumulates high levels of manganese ions, and this is believed to be correlated with the radiation resistance ability of this microorganism. The maintenance of manganese ion homeostasis in D. radiodurans remains to be investigated. Deinococcus radiodurans is an extreme bacterium known for its resistance to ionizing radiation (IR), ultraviolet (UV) radiation, oxidative stress, and desiccation [1,2]. It has been reported that D. radiodurans can recover from exposure to g-radiation at 15 kGy, a dose lethal to most life forms. IR can directly damage biomacromolecules and can produce reactive oxygen species (ROS) that can indirectly attack both proteins and DNA [3,4]. Cellular defense against ROS-induced protein and DNA damage is proposed to be important to the radiation resistance of D. radiodurans [5]. Daly and coworkers found that the Mn/Fe ratio of most IR-
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