Mn-peptides complexes involved in γ-radiation resistance in Deinococcus radiodurans

Deinococcus Radiodurans (Dr) is a bacterium which has drawn a lot of attention on its extraordinary radioprotective properties since its discovery in 1956. Different authors have reported that Mn-peptide complexes, isolated from Dr cell-free extract, could act as scavenging agents by neutralizing ROS molecules induced through radiation exposure [1]. In this study we have investigated the interaction between Mn(II) and two different peptides, DP1(DEHGTAVMLK) and DP2 (THMVLAKGED), as a model of the antioxidative mechanism in Dr. The amino acid composition of these peptides was chosen randomly on the basis of their natural abundance in the Dr protein-free cell extract (ultrafiltrate). We have focused our attention on the coordination of Mn(II) with DP1 and DP2 peptides by using NMR, EPR and ESI-MS techniques. Additionally, competition experiments have been done to study the equilibrium between Mn-peptides and Mnphosphate complexes, which, according to recent findings, could be a key point to explain the radiation resistance of Dr [2].