Manganese-peptide complexes involved in radioresistance in Deinococcus radiodurans bacterium

Deinococcus radiodurans (DR) is a bacterium extraordinary resistant to chronic radiation (50 Gy per hour) and acute doses (greater than 10 kGy). Although the biochemical basis of the radioprotective properties are still unknown, recent findings reported that Mn(II)- peptide complexes, isolated from DR cell-free extract, could act as scavenging agents by neutralizing ROS molecules induced through radiation exposure. Here we report the results of the interaction of Mn(II) and two peptides: DEHGTAVMLK and THMVLAKGED, as a model of the antioxidative mechanism in DR. The amino acid composition of the peptides was chosen randomly on the basis of their natural abundance in the DR cell-free extract. We have focused our attention on the coordination of Mn(II) with both peptides by using potentiometric titration and spectroscopic techniques (NMR, EPR and ESI-MS).