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Flexible aspartates propel iron to the ferroxidation sites along pathways stabilized by a conserved arginine in Dps proteins from Mycobacterium smegmatis

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Abstract

DNA-binding proteins under starvation (Dps) are dodecameric nano-compartments for iron oxidation and storage in bacterial cells. These proteins have roughly spherical structures with a hollow interior where iron is stored. Through mutational analysis of a conserved arginine residue in the second Dps protein from Mycobacterium smegmatis, we have identified residues which stabilize the interfaces between the iron entry and ferroxidation sites. Also, we have used X-ray crystallography to determine the structures of co-crystals of iron and Dps in varying proportions and compare the changes in these ligand-bound forms with respect to the apo-protein. The iron-loaded proteins of low, medium and high iron-bound forms were found to exhibit aspartate residues with alternate conformations, some of which could be directly linked to the sites of ferroxidation and iron entry. We conclude that the increased flexibility of aspartates in the presence of iron facilitates its movement from the entry site to the ferroxidaton site, and the two active sites are stabilized by the interactions of a conserved arginine residue R73.

Graphical abstract: Flexible aspartates propel iron to the ferroxidation sites along pathways stabilized by a conserved arginine in Dps proteins from Mycobacterium smegmatis

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Publication details

The article was received on 10 Jan 2017, accepted on 31 Mar 2017 and first published on 03 Apr 2017


Article type: Paper
DOI: 10.1039/C7MT00008A
Citation: Metallomics, 2017, Advance Article
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    Flexible aspartates propel iron to the ferroxidation sites along pathways stabilized by a conserved arginine in Dps proteins from Mycobacterium smegmatis

    S. M. Williams and D. Chatterji, Metallomics, 2017, Advance Article , DOI: 10.1039/C7MT00008A

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