Mitochondrial Bol1 and Bol3 function as assembly factors for specific iron-sulfur proteins

Assembly of mitochondrial iron-sulfur (Fe/S) proteins is a key process of cells, and defects cause many rare diseases. In the first phase of this pathway, ten Fe/S cluster (ISC) assembly components synthesize and insert [2Fe-2S] clusters. The second phase is dedicated to the assembly of [4Fe-4S] proteins, yet this part is poorly understood. Here, we characterize the BOLA family proteins Bol1 and Bol3 as specific mitochondrial ISC assembly factors that facilitate [4Fe-4S] cluster insertion into a subset of mitochondrial proteins such as lipoate synthase and succinate dehydrogenase. Bol1-Bol3 perform largely overlapping functions, yet cannot replace the ISC protein Nfu1 that also participates in this phase of Fe/S protein biogenesis. Bol1 and Bol3 form dimeric complexes with both monothiol glutaredoxin Grx5 and Nfu1. Complex formation differentially influences the stability of the Grx5-Bol-shared Fe/S clusters. Our findings provide the biochemical basis for explaining the pathological phenotypes of patients with mutations in BOLA3. DOI: http://dx.doi.org/10.7554/eLife.16673.00

Evolutionary conservation and in vitro reconstitution of microsporidian iron–sulfur cluster biosynthesis

This work was supported by Marie Curie Postdoctoral Fellowships to T.A.W., E. H. and S. L., a European Research Council Advanced Investigator Grant (ERC-2010-AdG-268701) to T.M.E., and a Wellcome Trust Programme Grant (number 045404) to T.M.E. and J.M.L. R.L. acknowledges generous financial support from Deutsche Forschungsgemeinschaft (SFB 593, SFB 987, GRK 1216, LI 415/5), LOEWE program of state Hessen, Max-Planck Gesellschaft, von Behring-Röntgen StiftungMicrosporidians are a diverse group of obligate intracellular parasites that have minimized their genome content and simplified their sub-cellular structures by reductive evolution. Functional studies are limited because we lack reliable genetic tools for their manipulation. Here, we demonstrate that the cristae-deficient mitochondrion (mitosome) of the microsporidian Trachipleistophora hominis is the functional site of iron-sulphur cluster (ISC) assembly, which we suggest is the essential task of this organelle. Cell fractionation, fluorescence imaging and fine-scale immunoelectron microscopy demonstrate that mitosomes contain a complete pathway for [2Fe-2S] cluster biosynthesis that we biochemically reconstituted using purified recombinant mitosomal ISC proteins. Reconstitution proceeded as rapidly and efficiently as observed for yeast or fungal mitochondrial ISC components. Core components of the T. hominis cytosolic iron-sulphur protein assembly (CIA) pathway were also identified including the essential Cfd1-Nbp35 scaffold complex that assembles a [4Fe-4S] cluster as shown by spectroscopic methods in vitro. Phylogenetic analyses reveal that both the ISC and CIA biosynthetic pathways are predominantly bacterial, but their cytosolic and nuclear target Fe/S proteins are mainly archaeal. This mixed evolutionary history of the Fe/S-related proteins and pathways, and their strong conservation among highly reduced parasites, provides additional compelling evidence for the ancient chimeric ancestry of eukaryotes.Publisher PDFPeer reviewe

Modelowanie numeryczne belek żelbetowych z uwzględnieniem rzeczywistego rozmieszczenia zbrojenia

The article presents comparison of the results obtained from reinforced concrete beams experimental studies with the use of ARAMIS system (digital image correlation) with the results gained from numerical modeling. During studies, deviation from the plane of reinforced concrete beams was observed. Inventory of rebars positions in cross-section of this beams showed significant deviations. Analysis carried out in the work [1] revealed the impact of improperly embedded longitudinal reinforcement on the occurrence of horizontal displacements. Based on the collected data, numerical models of two selected reinforced concrete beams with correct and incorrect positon of the reinforcing bars were made using the Concrete Damaged Plasticity model in Abaqus software. It has been shown that premature interruption of the calculation appeared in models taking into account deviations in the position of reinforcing bars. However, the occurrence of horizontal displacements was still confirmed by numerical model for beams with incorrect positioning of rebars.W artykule przedstawiono porównanie wyników badań eksperymentalnych belek żelbetowych z wykorzystaniem systemu ARAMIS (korelacja obrazu cyfrowego) z wynikami uzyskanymi w wyniku modelowania numerycznego. W wykonanych badaniach zaobserwowane zostało odchylenie z płaszczyzny belek żelbetowych, spowodowane niezgodnym z projektem rozmieszczeniem prętów zbrojenia, co potwierdzono w pracy [1]. Inwentaryzacja położenia prętów zbrojeniowych w przekroju poprzecznym belek wykazała ich znaczne odchylenia. Na podstawie zebranych danych, w oprogramowaniu Abaqus, przy użyciu modelu Concrete Damaged Plasticity, wykonano numeryczne modele dwóch wybranych belek żelbetowych z prawidłowym oraz nieprawidłowym rozmieszczeniem prętów. Stwierdzono przedwczesne przerwanie obliczeń dla modeli uwzględniających odchylenie w położeniu prętów zbrojeniowych. Mimo to opracowany model numeryczny potwierdza występowanie przemieszczeń poziomych w belkach z niewłaściwym rozmieszczeniem prętów

A Fatal Mitochondrial Disease Is Associated with Defective NFU1 Function in the Maturation of a Subset of Mitochondrial Fe-S Proteins

We report on ten individuals with a fatal infantile encephalopathy and/or pulmonary hypertension, leading to death before the age of 15 months. Hyperglycinemia and lactic acidosis were common findings. Glycine cleavage system and pyruvate dehydrogenase complex (PDHC) activities were low. Homozygosity mapping revealed a perfectly overlapping homozygous region of 1.24 Mb corresponding to chromosome 2 and led to the identification of a homozygous missense mutation (c.622G>T) in NFU1, which encodes a conserved protein suggested to participate in Fe-S cluster biogenesis. Nine individuals were homozygous for this mutation, whereas one was compound heterozygous for this and a splice-site (c.545+5G>A) mutation. The biochemical phenotype suggested an impaired activity of the Fe-S enzyme lipoic acid synthase (LAS). Direct measurement of protein-bound lipoic acid in individual tissues indeed showed marked decreases. Upon depletion of NFU1 by RNA interference in human cell culture, LAS and, in turn, PDHC activities were largely diminished. In addition, the amount of succinate dehydrogenase, but no other Fe-S proteins, was decreased. In contrast, depletion of the general Fe-S scaffold protein ISCU severely affected assembly of all tested Fe-S proteins, suggesting that NFU1 performs a specific function in mitochondrial Fe-S cluster maturation. Similar biochemical effects were observed in Saccharomyces cerevisiae upon deletion of NFU1, resulting in lower lipoylation and SDH activity. Importantly, yeast Nfu1 protein carrying the individuals' missense mutation was functionally impaired. We conclude that NFU1 functions as a late-acting maturation factor for a subset of mitochondrial Fe-S proteins