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DNA binding proteins under starved conditions (Dps)

DNA-binding proteins from starved cells (Dps)
Dps have been described only in prokaryotes and have been proposed to have an important role on protection of DNA from reactive oxygen species. Dps proteins can have a dual function: iron storage using hydrogen peroxide to oxidize ferrous ion, and at the same time protecting the DNA from damage. Dps are structurally similar to the ferritin superfamily; however they are composed by 12 subunits instead of the typical 24. The dodecamer is formed as a hollow sphere with a cavity used to store iron, which is oxidized in the ferroxidase center located on the two-fold axis. The Dps proteins, so far known, are structurally conserved, differing mainly on the N- or C-terminal extensions; in fact, these regions have been proposed to be responsible for the protein-DNA interaction. This interaction occurs without any sequence specificity, being mainly assured by the positively charged residues present on those extensions. The function of this family of proteins is as yet not fully understood, being apparently dependent on the organism. In Escherichia coli it has been shown that the protein plays a major role in tight compaction of nucleiod. Different examples have been reported of Dps-proteins that have been correlated with virulence of bacterial infections, such as in Salmonella enterica, Borrelia burgdorferi or Campylobacter jejuni.
I am currently studying the two Dps from the radiation resistant organism Deinococcus radiodurans. I have already determined the high resolution crystal structures of the two Dps, DrDps1 (DR2263) and DrDps2 (DRB0092) in two different states: apo-form and in complex with iron. In general terms, both proteins share the same overall structure with other members of the family: a hollow sphere with outer and interior shell diameters of 90 Å and 40 Å respectively, comprising 12 identical subunits. Both DrDps proteins have unique long N-terminal extensions when compared to the other family members known to date.
My aim under this project is to understand the cellular mechanism of how the DNA protection occurs and the possible linked role of iron storage. The results will elucidate the mechanisms underlying oxidative stress response systems, in which Dps proteins are involved, and in which DNA is protected and preserved from damage.

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