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).