Role of Dps1 and Dps2 in reactive oxygen species tolerance in Deinococcus radiodurans

Abstract

Deinococcus radiodurans is an extremophilic bacterium, capable of enduring large doses of ionizing radiation, oxidative stress and prolonged periods of desiccation. D. radiodurans is also fairly unique in that it encodes two Dps (DNA protection during starvation) proteins, Dps1 and Dps2. We have characterized the Dps homologs and a comparison of their functionality is reported. Dps2 is able oxidize and sequester Fe2+ within its protein core. Also, Dps2 binds DNA, although with an apparent lower affinity than Dps1. Furthermore, Dps2 can protect DNA from reactive oxygen species, but is unable to protect DNA from endonucleases, while the converse is true for Dps1. Dps1 is solely capable of condensing genomic DNA in vivo, while notably Dps2 is non‐cytoplasmically localized, a characteristic yet seen of Dps proteins. Dps2 expression levels were shown to remain static throughout the cell cycle, in contrast to the massive upregulation seen for E. coli Dps. These findings suggest that Dps1 may serve a role in iron homeostasis and nucleoid organization, while Dps2 may protect D. radiodurans from exogenous ROS.