Abstract
We characterized two interrelated proteins from the Deinococcus geothermalis strain with regard to the role of DNA-binding and protection, such as a novel Dps, Dgeo_0257, and a Dps orthologous protein, Dgeo_0281. Despite the lack of conserved amino acid sequence for ferroxidase activity, Dgeo_0257 exhibited high DNA-binding affinity and formed a dodecameric conformation. In contrast, Dgeo_0281 protein showed less effective DNA-binding and was mainly observed monomeric or dimeric forms. Electrophoretic mobility shift assay showed that both purified proteins are non-specifically bound to DNA to protect against DNA degradation and the properties of Dps responding to specific metal ions. In the presence of ferrous and ferric ions, Dgeo_0257 or Dgeo_0281 protein does not readily bind to DNA. However, in Zn and Mn ions are present, both proteins had more stable DNA-binding. From the Dps gene disrupted mutant test, each showed a higher sensitivity to oxidative stress than the wild-type strain. In addition, the expression level of each gene was correlated with the presence of each other. In this study, we characterized and confirmed the functional roles of Dgeo_0257 for sensing metal ions and binding to DNAs along with the Dps orthologous Dgeo_0281. Based on various observational evidence, we propose that Dgeo_0257 is a novel Dps protein with no ferroxidase activity.