The Di-iron RIC Protein (YtfE) of Escherichia coli Interacts with the DNA-Binding Protein from Starved Cells (Dps) To Diminish RIC Protein-Mediated Redox Stress.

The RIC (repair of iron clusters) protein of is a di-iron hemerythrin-like protein that has a proposed function in repairing stress-damaged iron-sulfur clusters. In this work, we performed a bacterial two-hybrid screening to search for RIC-protein interaction partners in As a result, the NA-binding rotein from tarved cells (Dps) was identified, and its potential interaction with RIC was tested by bacterial adenylate cyclase-based two-hybrid (BACTH) system, bimolecular fluorescence complementation, and pulldown assays. Using the activity of two Fe-S-containing enzymes as indicators of cellular Fe-S cluster damage, we observed that strains with single deletions of or have significantly lower aconitase and fumarase activities. In contrast, the double mutant strain displayed no loss of aconitase and fumarase activity with respect to that of the wild type. Additionally, while complementation of the double mutant with led to a severe loss of aconitase activity, this effect was no longer observed when a gene encoding a di-iron site variant of the RIC protein was employed. The mutant exhibited a large increase in reactive oxygen species (ROS) levels, but this increase was eliminated when was also inactivated. Absence of other iron storage proteins, or of peroxidase and catalases, had no impact on RIC-mediated redox stress induction. Hence, we show that RIC interacts with Dps in a manner that serves to protect from RIC protein-induced ROS. The mammalian immune system produces reactive oxygen and nitrogen species that kill bacterial pathogens by damaging key cellular components, such as lipids, DNA, and proteins. However, bacteria possess detoxifying and repair systems that mitigate these deleterious effects. The RIC (repair of iron clusters) protein is a di-iron hemerythrin-like protein that repairs stress-damaged iron-sulfur clusters. Dps is an iron storage protein of the ferritin superfamily with DNA-binding capacity that protects cells from oxidative stress. This work shows that the RIC and Dps proteins interact in a fashion that counters RIC protein-induced reactive oxygen species (ROS). Altogether, we provide evidence for the formation of a new bacterial protein complex and reveal a novel contribution for Dps in bacterial redox stress protection.