title: A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery.
abstract: Cells contain hundreds of proteins that require iron cofactors for activity. Iron cofactors are synthesized in the cell, but the pathways involved in distributing heme, iron-sulfur clusters, and ferrous/ferric ions to apoproteins remain incompletely defined. In particular, cytosolic monothiol glutaredoxins and BolA-like proteins have been identified as [2Fe-2S]-coordinating complexesin vitroand iron-regulatory proteins in fungi, but it is not clear how these proteins function in mammalian systems or how this complex might affect Fe-S proteins or the cytosolic Fe-S assembly machinery. To explore these questions, we use quantitative immunoprecipitation and live cell proximity-dependent biotinylation to monitor interactions between Glrx3, BolA2, and components of the cytosolic iron-sulfur cluster assembly system. We characterize cytosolic Glrx3·BolA2 as a [2Fe-2S] chaperone complex in human cells. Unlike complexes formed by fungal orthologs, human Glrx3-BolA2 interaction required the coordination of Fe-S clusters, whereas Glrx3 homodimer formation did not. Cellular Glrx3·BolA2 complexes increased 6-8-fold in response to increasing iron, forming a rapidly expandable pool of Fe-S clusters. Fe-S coordination by Glrx3·BolA2 did not depend on Ciapin1 or Ciao1, proteins that bind Glrx3 and are involved in cytosolic Fe-S cluster assembly and distribution. Instead, Glrx3 and BolA2 bound and facilitated Fe-S incorporation into Ciapin1, a [2Fe-2S] protein functioning early in the cytosolic Fe-S assembly pathway. Thus, Glrx3·BolA is a [2Fe-2S] chaperone complex capable of transferring [2Fe-2S] clusters to apoproteins in human cells.
authors: From the Genetics and Metabolism Section, Liver Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892 and.
authors: Avery G
authors: AG
authors: Frey
authors: From the Genetics and Metabolism Section, Liver Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892 and.
authors: Daniel J
authors: DJ
authors: Palenchar
authors: the College of Medicine, Ohio State University, Columbus, Ohio 43210.
authors: Justin D
authors: JD
authors: Wildemann
authors: From the Genetics and Metabolism Section, Liver Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892 and Carolinep@mail.nih.gov.
authors: Caroline C
authors: CC
authors: Philpott
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*
chemical_list: C533596:BOLA2 protein, human; D002352:Carrier Proteins; C404105:GLRX3 protein, human; D007506:Iron-Sulfur Proteins; D011506:Proteins
keywords: BolA2; Ciapin1; Glrx3; Ndor1; biotin; iron; iron-sulfur protein; metal homeostasis; metal ion-protein interaction; metalloprotein