Dataset Information

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 complexes in vitro and 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.

SUBMITTER: Frey AG

PROVIDER: S-EPMC5077177 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery.

Frey Avery G AG Palenchar Daniel J DJ Wildemann Justin D JD Philpott Caroline C CC

The Journal of biological chemistry 20160812 43

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 complexes <i>in vitro</i> and iron-regulatory proteins in fungi, but it is not clear how these proteins function in mammali ...[more]

PMID: 27519415

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Project description:The cytosolic iron/sulfur cluster assembly (CIA) machinery is responsible for the assembly of cytosolic and nuclear iron/sulfur clusters, cofactors that are vital for all living cells. This machinery is uniquely found in eukaryotes and consists of at least eight proteins in opisthokont lineages, such as animals and fungi. We sought to identify and characterize homologues of the CIA system proteins in the anaerobic stramenopile parasite Blastocystis sp. strain NandII. We identified transcripts encoding six of the components-Cia1, Cia2, MMS19, Nbp35, Nar1, and a putative Tah18-and showed using immunofluorescence microscopy, immunoelectron microscopy, and subcellular fractionation that the last three of them localized to the cytoplasm of the cell. We then used comparative genomic and phylogenetic approaches to investigate the evolutionary history of these proteins. While most Blastocystis homologues branch with their eukaryotic counterparts, the putative Blastocystis Tah18 seems to have a separate evolutionary origin and therefore possibly a different function. Furthermore, our phylogenomic analyses revealed that all eight CIA components described in opisthokonts originated before the diversification of extant eukaryotic lineages and were likely already present in the last eukaryotic common ancestor (LECA). The Nbp35, Nar1 Cia1, and Cia2 proteins have been conserved during the subsequent evolutionary diversification of eukaryotes and are present in virtually all extant lineages, whereas the other CIA proteins have patchy phylogenetic distributions. Cia2 appears to be homologous to SufT, a component of the prokaryotic sulfur utilization factors (SUF) system, making this the first reported evolutionary link between the CIA and any other Fe/S biogenesis pathway. All of our results suggest that the CIA machinery is an ubiquitous biosynthetic pathway in eukaryotes, but its apparent plasticity in composition raises questions regarding how it functions in nonmodel organisms and how it interfaces with various iron/sulfur cluster systems (i.e., the iron/sulfur cluster, nitrogen fixation, and/or SUF system) found in eukaryotic cells.

Dataset Information

A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery.

Publications

A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery.

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