Escherichia coli RIC Is Able to Donate Iron to Iron-Sulfur Clusters

Abstract

Escherichia coli RIC (Repair of Iron Centers) is a diiron protein previously reported to be involved in the repair of iron-sulfur proteins damaged by oxidative or nitrosative stresses, and proposed to act as an iron donor. This possible role of RIC was now examined specifically by evaluating its ability to donate iron ions to apo-iron-sulfur proteins, determining the iron binding constants and assessing the lability of its iron ions. We show, by UV-visible, EPR and resonance Raman spectroscopies that RIC may participate in the synthesis of an iron-sulfur cluster in the apo-forms of the spinach ferredoxin and IscU when in the presence of the sulfide donating system IscS and L-cysteine. Iron binding assays allowed determining the as-isolated and fully reduced RIC dissociation constants for the ferric and ferrous iron of 10−27 M and 10−13 M, respectively. Mössbauer studies revealed that the RIC iron ions are labile, namely when the center is in the mixed-valence redox form as compared with the (μ-oxo) diferric one. Altogether, these results suggest that RIC is capable of delivering iron for the formation of iron-sulfur clusters.

Cellular responses to reactive oxygen species are predicted from molecular mechanisms

“…Second, we describe Fe-S cluster repair. We assume that yggX (15) or ytfE (16) repairs Fe-S clusters using NADH as the electron donor and define the net repair reaction: [3Fe-4S] 1+ + Fe 2+ + NADH → [4Fe-4S] 2+ + NAD + .…”

“…A possible explanation is that M. tuberculosis's ISC scaffold proteins are less sensitive to ROS than those in E. coli or are repaired. However, E. coli also possesses several putative Fe-S cluster repair genes, including ygfZ (33), yggX (15), and ytfE (16). Overall, gaps exist in our understanding of the costbenefit tradeoffs between ISC and SUF under ROS stress.…”

Insights into the structure of the diiron site of RIC from Escherichia coli

“…Based on extended X-ray absorption fine structure (EXAFS) data, the centre was proposed to be coordinated by histidines and one or two l-carboxylate bridges from aspartate or glutamate residues, and that the Fe-Fe distance increases upon reduction with the concomitant decrease of the number of coordinated ligands [6]. Recently, Mössbauer studies revealed that the iron ions of the RIC centre are more labile in the mixed-valence Fe(III)-Fe(II) redox state when compared with the l-oxo-diferric form [10]. Furthermore, it was shown that E. coli RIC is able to deliver iron, most likely in the ferrous state, for the assembly of the Fe-S clusters of spinach apo-ferredoxin and E. coli IscU [10].…”

“…Recently, Mössbauer studies revealed that the iron ions of the RIC centre are more labile in the mixed-valence Fe(III)-Fe(II) redox state when compared with the l-oxo-diferric form [10]. Furthermore, it was shown that E. coli RIC is able to deliver iron, most likely in the ferrous state, for the assembly of the Fe-S clusters of spinach apo-ferredoxin and E. coli IscU [10]. These data suggest that E. coli RIC may also act as an iron donor under non-stress conditions, which is in line with the lower aconitase and fumarase activities exhibited by non-stressed E. coli ric mutant cells.…”

Hemerythrin is required for Aeromonas hydraphlia to survive in the macrophages of Anguilla japonica

“…Justino et al (2007) and Vine et al (2010) also reported that the E. coli Hr-like protein YtfE, which has the same conserved domain as Hr, confers protection against H 2 O 2 stress by repairing degraded iron-sulfur clusters. Therefore, we hypothesize that the Hr protein has the same function as YtfE in repairing damage to iron-sulfur clusters and potentially by donating iron to iron-sulfur clusters (Nobre et al, 2014).…”