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The eukaryotic P loop NTPase Nbp35: an essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery.

ABSTRACT: Soluble P loop NTPases represent a large protein family and are involved in diverse cellular functions. Here, we functionally characterized the first member of the Mrp/Nbp35 subbranch of this family, the essential Nbp35p of Saccharomyces cerevisiae. The protein resides in the cytosol and nucleus and carries an Fe/S cluster at its N terminus. Assembly of the Fe/S cluster requires the mitochondrial Fe/S cluster (ISC)-assembly and -export machineries. Depletion of Nbp35p strongly impairs the activity of the cytosolic Fe/S protein, isopropylmalate isomerase (Leu1p), whereas mitochondrial Fe/S enzymes are unaffected. Moreover, defects in the de novo maturation of various cytosolic and nuclear Fe/S proteins were observed in the absence of Nbp35p, demonstrating the functional involvement of Nbp35p in the biogenesis of extramitochondrial Fe/S proteins. Furthermore, Nbp35p genetically interacts with the closely similar P loop NTPase, Cfd1p, and the hydrogenase-like Nar1p, both of which were recently shown to perform a crucial function in cytosolic and nuclear Fe/S protein biogenesis. Hence, our study suggests that eukaryotic Nbp35 NTPases function in Fe/S protein maturation. The findings provide strong evidence for the existence of a highly conserved and essential machinery dedicated to assembling cytosolic and nuclear Fe/S proteins.

SUBMITTER: Hausmann A

PROVIDER: S-EPMC552912 | biostudies-literature | 2005 Mar

REPOSITORIES: biostudies-literature

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The eukaryotic P loop NTPase Nbp35: an essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery.

Hausmann Anja A Aguilar Netz Daili J DJ Balk Janneke J Pierik Antonio J AJ Mühlenhoff Ulrich U Lill Roland R

Proceedings of the National Academy of Sciences of the United States of America 20050222 9

Soluble P loop NTPases represent a large protein family and are involved in diverse cellular functions. Here, we functionally characterized the first member of the Mrp/Nbp35 subbranch of this family, the essential Nbp35p of Saccharomyces cerevisiae. The protein resides in the cytosol and nucleus and carries an Fe/S cluster at its N terminus. Assembly of the Fe/S cluster requires the mitochondrial Fe/S cluster (ISC)-assembly and -export machineries. Depletion of Nbp35p strongly impairs the activi ...[more]

PMID: 15728363

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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

The eukaryotic P loop NTPase Nbp35: an essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery.

Publications

The eukaryotic P loop NTPase Nbp35: an essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery.

Similar Datasets

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