Hundreds of cellular proteins require iron cofactors for activity, and cells express systems for their assembly and distribution. Molecular details of the cytosolic iron pool used for iron cofactors are lacking, but iron chaperones of the poly(rC)-binding protein (PCBP) family play a key role in ferrous ion distribution. Here we show that, in cells and in vitro, PCBP1 coordinates iron via conserved cysteine and glutamate residues and a molecule of noncovalently bound glutathione (GSH). Proteomics analysis of PCBP1-interacting proteins identified BolA2, which functions, in complex with Glrx3, as a cytosolic [2Fe–2S] cluster chaperone. The Fe–GSH-bound form of PCBP1 complexes with cytosolic BolA2 via a bridging Fe ligand. Biochemical analysis of PCBP1 and BolA2, in cells and in vitro, indicates that PCBP1–Fe–GSH–BolA2 serves as an intermediate complex required for the assembly of [2Fe–2S] clusters on BolA2–Glrx3, thereby linking the ferrous iron and Fe–S distribution systems in cells.
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This work was supported by the Intramural Research Program of the National Institutes of Diabetes and Digestive and Kidney Diseases and the Office of Dietary Supplements, Office of the Director, National Institutes of Health. J.A.W. is supported by NIH grant nos. GM089778 and GM112763. We thank C. Outten (University of South Carolina) for plasmids and T. Stemmler (Wayne State University) for plasmids and helpful discussions.
The authors declare no competing interests.
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