title: The Escherichia coli BolA Protein IbaG Forms a Histidine-Ligated [2Fe-2S]-Bridged Complex with Grx4.
abstract: Two ubiquitous protein families have emerged as key players in iron metabolism, the CGFS-type monothiol glutaredoxins (Grxs) and the BolA proteins. Monothiol Grxs and BolA proteins form heterocomplexes that have been implicated in Fe-S cluster assembly and trafficking. The Escherichia coli genome encodes members of both of these proteins families, namely, the monothiol glutaredoxin Grx4 and two BolA family proteins, BolA and IbaG. Previous work has demonstrated that E. coli Grx4 and BolA interact as both apo and [2Fe-2S]-bridged heterodimers that are spectroscopically distinct from [2Fe-2S]-bridged Grx4 homodimers. However, the physical and functional interactions between Grx4 and IbaG are uncharacterized. Here we show that co-expression of Grx4 with IbaG yields a [2Fe-2S]-bridged Grx4-IbaG heterodimer. In vitro interaction studies indicate that IbaG binds the [2Fe-2S] Grx4 homodimer to form apo Grx4-IbaG heterodimer as well as the [2Fe-2S] Grx4-IbaG heterodimer, altering the cluster stability and coordination environment. Additionally, spectroscopic and mutagenesis studies provide evidence that IbaG ligates the Fe-S cluster via the conserved histidine that is present in all BolA proteins and by a second conserved histidine that is present in the H/C loop of two of the four classes of BolA proteins. These results suggest that IbaG may function in Fe-S cluster assembly and trafficking in E. coli as demonstrated for other BolA homologues that interact with monothiol Grxs.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina , 631 Sumter Street, Columbia, South Carolina 29208, United States.
authors.forename: Adrienne C
authors.initials: AC
authors.lastname: Dlouhy
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina , 631 Sumter Street, Columbia, South Carolina 29208, United States.
authors.forename: Haoran
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina , 631 Sumter Street, Columbia, South Carolina 29208, United States.
authors.forename: Angela-Nadia
authors.initials: AN
authors.lastname: Albetel
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Daphne T
authors.initials: DT
authors.lastname: Mapolelo
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Sajini
authors.initials: S
authors.lastname: Randeniya
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Holland
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Johnson
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina , 631 Sumter Street, Columbia, South Carolina 29208, United States.
authors.forename: Caryn E
authors.initials: CE
authors.lastname: Outten
mesh_terms: D002151:Calorimetry; D002942:Circular Dichroism; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008970:Molecular Weight; D013057:Spectrum Analysis / Q000379:methods; D014157:Transcription Factors / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; C574379:IbaG protein, E coli; D007506:Iron-Sulfur Proteins; D014157:Transcription Factors; D006639:Histidine