Antioxidant Dps protein from the thermophilic cyanobacterium Thermosynechococcus elongatus

Abstract

DNA‐binding proteins from starved cells (Dps proteins) protect bacteria primarily from oxidative damage. They are composed of 12 identical subunits assembled with 23‐symmetry to form a compact cage‐like structure known to be stable at temperatures > 70 °C and over a wide pH range. Thermosynechococcus elongatus Dps thermostability is increased dramatically relative to mesophilic Dps proteins. Hydrophobic interactions at the dimeric and trimeric interfaces called Dps‐like are replaced by salt bridges and hydrogen bonds, a common strategy in thermophiles. Moreover, the buried surface area at the least‐extended Dps‐like interface is significantly increased. A peculiarity of T. elongatus Dps is the presence of a chloride ion coordinated with threefold symmetry‐related arginine residues lining the opening of the Dps‐like pore toward the internal cavity. T. elongatus Dps conserves the unusual intersubunit ferroxidase centre that allows the Dps protein family to oxidize Fe(II) with hydrogen peroxide, thereby inhibiting free radical production via Fenton chemistry. This catalytic property is of special importance in T. elongatus (which lacks the catalase gene) in the protection of DNA and photosystems I and II from hydrogen peroxide‐mediated oxidative damage.

Conserved histidine residues at the ferroxidase centre of the Campylobacter jejuni Dps protein are not strictly required for metal binding and oxidation

“…3). These data are in agreement with the results reported for other Dps family proteins (Franceschini et al, 2006;Zhao et al, 2002). However, they are contrary to the results obtained using an Nterminal 10|His-tagged form of CjDps (Huergo et al, 2013).…”

“…1b, c). The Dps FOC is known to contain two metal-binding sites with a different affinity for Fe 2+ ions (Franceschini et al, 2006 (Chiancone & Ceci, 2010). In Escherichia coli Dps, the reaction rate increases 100-fold in the presence of H 2 O 2 (Zhao et al, 2002).…”

“…The archetypical function of Dps seems to be DNA protection against hydroxyl radicals that are produced when Fe 2+ and H 2 O 2 combine (Zhao et al, 2002). DNA protection occurs indirectly via iron oxidation and storage; furthermore, some Dps family members can physically protect DNA through the formation of Dps-DNA complexes, independent of the DNA sequence (Franceschini et al, 2006). Dps proteins are a subfamily of ferritins composed of 12 identical subunits that are assembled into a spherical protein shell (Fig.…”

Biomimetic Materials Synthesis from Ferritin-Related, Cage-Shaped Proteins

“…In H. pylori Dps, D. radiodurans Dps1 and A. tumefaciens Dps structures, only the A site contains iron whereas the B site contains a water molecule (Ceci et al, 2003;Romão et al, 2006;Zanotti et al, 2002). In E. coli Dps (Grant et al, 1998) and T. elongatus Dps both sites are occupied by two water molecules (Franceschini et al, 2006). These data indicate that the two metal binding sites A and B have different affinity for iron, and that the second metal coordination shell, formed by residues that are not directly in contact with the metal but interact with metal binding site residues, may influence the affinity for iron.…”

The Iron-Binding Protein Dps2 Confers Peroxide Stress Resistance on Bacillus anthracis

“…Dps1 and Dps2 have been extensively characterized in vitro (26,29,37). These studies have shown that their reactivity with H 2 O 2 and O 2 is in striking contrast to that of the Dps proteins characterized in other organisms (26), which generally use H 2 O 2 as the preferred iron oxidant with an ϳ100-to 1,000-fold preference over O 2 (11,38,41 (26), and it may function as both a detoxifying enzyme and an iron storage protein.…”