7aqs
From Proteopedia
Crystal structure of E. coli DPS in space group P1
Structural highlights
FunctionDPS_ECOLI During stationary phase, binds the chromosome non-specifically, forming a highly ordered and stable dps-DNA co-crystal within which chromosomal DNA is condensed and protected from diverse damages. It protects DNA from oxidative damage by sequestering intracellular Fe(2+) ion and storing it in the form of Fe(3+) oxyhydroxide mineral, which can be released after reduction. One hydrogen peroxide oxidizes two Fe(2+) ions, which prevents hydroxyl radical production by the Fenton reaction. Dps also protects the cell from UV and gamma irradiation, iron and copper toxicity, thermal stress and acid and base shocks. Also shows a weak catalase activity.[1] [2] [3] [4] Publication Abstract from PubMedColicins are bacterial toxins targeting Gram-negative bacteria, including E. coli and related Enterobacteriaceae strains. Some colicins form ion-gated pores in the inner membrane of attacked bacteria that are lethal to their target. Colicin Ia was the first pore-forming E. coli toxin, for which a high-resolution structure of the monomeric full-length protein was determined. It is so far also the only colicin, for which a low-resolution structure of its membrane-inserted pore was reported by negative-stain electron microscopy. Resolving this structure at the atomic level would allow an understanding of the mechanism of toxin pore formation. Here, we report an observation that we made during an attempt to determine the Colicin Ia pore structure at atomic resolution. Colicin Ia was natively expressed by mitomycin-C induction under a native SOS promotor and purified following published protocols. The visual appearance in the electron microscope of negatively stained preparations and the lattice parameters of 2D crystals obtained from the material were highly similar to those reported earlier resulting from the same purification protocol. However, a higher-resolution structural analysis revealed that the protein is Dps (DNA-binding protein from starved cells), a dodecameric E. coli protein. This finding suggests that the previously reported low-resolution structure of a "Colicin Ia oligomeric pore" actually shows Dps. Identification of a Dps contamination in Mitomycin-C-induced expression of Colicin Ia.,Pipercevic J, Jakob RP, Righetto RD, Goldie KN, Stahlberg H, Maier T, Hiller S Biochim Biophys Acta Biomembr. 2021 Jul 1;1863(7):183607. doi: , 10.1016/j.bbamem.2021.183607. Epub 2021 Mar 26. PMID:33775657[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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