Dataset Information

Divergence of Erv1-associated mitochondrial import and export pathways in trypanosomes and anaerobic protists.

ABSTRACT: In yeast (Saccharomyces cerevisiae) and animals, the sulfhydryl oxidase Erv1 functions with Mia40 in the import and oxidative folding of numerous cysteine-rich proteins in the mitochondrial intermembrane space (IMS). Erv1 is also required for Fe-S cluster assembly in the cytosol, which uses at least one mitochondrially derived precursor. Here, we characterize an essential Erv1 orthologue from the protist Trypanosoma brucei (TbERV1), which naturally lacks a Mia40 homolog. We report kinetic parameters for physiologically relevant oxidants cytochrome c and O(2), unexpectedly find O(2) and cytochrome c are reduced simultaneously, and demonstrate that efficient reduction of O(2) by TbERV1 is not dependent upon a simple O(2) channel defined by conserved histidine and tyrosine residues. Massive mitochondrial swelling following TbERV1 RNA interference (RNAi) provides evidence that trypanosome Erv1 functions in IMS protein import despite the natural absence of the key player in the yeast and animal import pathways, Mia40. This suggests significant evolutionary divergence from a recently established paradigm in mitochondrial cell biology. Phylogenomic profiling of genes also points to a conserved role for TbERV1 in cytosolic Fe-S cluster assembly. Conversely, loss of genes implicated in precursor delivery for cytosolic Fe-S assembly in Entamoeba, Trichomonas, and Giardia suggests fundamental differences in intracellular trafficking pathways for activated iron or sulfur species in anaerobic versus aerobic eukaryotes.

SUBMITTER: Basu S

PROVIDER: S-EPMC3571301 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Divergence of Erv1-associated mitochondrial import and export pathways in trypanosomes and anaerobic protists.

Basu Somsuvro S Leonard Joanne C JC Desai Nishal N Mavridou Despoina A I DA Tang Kong Ho KH Goddard Alan D AD Ginger Michael L ML Lukeš Julius J Allen James W A JW

Eukaryotic cell 20121221 2

In yeast (Saccharomyces cerevisiae) and animals, the sulfhydryl oxidase Erv1 functions with Mia40 in the import and oxidative folding of numerous cysteine-rich proteins in the mitochondrial intermembrane space (IMS). Erv1 is also required for Fe-S cluster assembly in the cytosol, which uses at least one mitochondrially derived precursor. Here, we characterize an essential Erv1 orthologue from the protist Trypanosoma brucei (TbERV1), which naturally lacks a Mia40 homolog. We report kinetic parame ...[more]

PMID: 23264646

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Project description:Upon nitrogen starvation, the basidiomycete Ustilago maydis, which causes smut disease on corn, secretes amphipathic glycolipids, including mannosylerythritol lipids (MELs). MELs consist of a carbohydrate core whose mannosyl moiety is both acylated with fatty acids of different lengths and acetylated. Here, we report the transport of MELs into and out of the cell depending on the transport protein Mmf1, which belongs to the major facilitator superfamily. Analysis of mmf1 mutants and mutants lacking the acetyltransferase Mat1 revealed that Mmf1 is necessary for the export of acetylated MELs, while MELs without an acetyl group are secreted independently of this transporter. Upon deletion of mmf1, we detected novel MEL species lacking the acyl side chain at C-3'. With the help of feeding experiments, we demonstrate that MELs are taken up by U. maydis in an mmf1-independent manner. This leads to catabolism or rearrangement of acetyl and acyl side groups and subsequent secretion. The catabolism of MELs involves the presence of Mac2, an enzyme required for MEL biosynthesis. In cocultivation experiments, mutual exchange of MELs between different mutants was observed. Thus, we propose a novel function for fungal glycolipids as an external carbon storage. IMPORTANCE Fungi produce and secrete various secondary metabolites that can act as weapons against competitors, help in accessing nutrients, or assist in development and communication. One group of secondary metabolites are surface-active glycolipids, which have significant biotechnological potential as biodegradable detergents. While the biosynthesis of several fungal biosurfactants is well characterized, their biological functions and transport routes are less understood. We developed a cocultivation assay to show that a class of glycolipids from Ustilago maydis called mannosylerythritol lipids (MELs) can be exchanged between cells and modified or even degraded by recipient cells. Feeding assays with purified MELs led to similar results. These data provide insight into the surprising biological role of MELs as putative external carbon sources. Applying feeding and cocultivation experiments on MEL biosynthesis mutants turned out to be a valuable strategy for systematically studying the import routes and degradation pathways of glycolipids. By using these assays, we demonstrate the function of the transport protein Mmf1 as a specific exporter of acetylated MELs. We propose that these assays may be applied more generally, thereby opening novel areas of research.

Dataset Information

Divergence of Erv1-associated mitochondrial import and export pathways in trypanosomes and anaerobic protists.

Publications

Divergence of Erv1-associated mitochondrial import and export pathways in trypanosomes and anaerobic protists.

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