Mammalian Frataxin: An Essential Function for Cellular Viability through an Interaction with a Preformed ISCU/NFS1/ISD11 Iron-Sulfur Assembly Complex

Frataxin, the mitochondrial protein deficient in Friedreich ataxia, a rare autosomal recessive neurodegenerative disorder, is thought to be involved in multiple iron-dependent mitochondrial pathways. In particular, frataxin plays an important role in the formation of iron-sulfur (Fe-S) clusters biogenesis.. Fe-S cluster biosynthesis

Genome Sequence of Azotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

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Multiple I-Type Lysozymes in the Hydrothermal Vent Mussel Bathymodiolus azoricus and Their Role in Symbiotic Plasticity

International audienceThe aim of this study was first to identify lysozymes paralogs in the deep sea mussel Bathy-modiolus azoricus then to measure their relative expression or activity in different tissue or conditions. B. azoricus is a bivalve that lives close to hydrothermal chimney in the Mid-Atlantic Ridge (MAR). They harbour in specialized gill cells two types of endosymbiont (gram— bacteria): sulphide oxidizing bacteria (SOX) and methanotrophic bacteria (MOX). This association is thought to be ruled by specific mechanism or actors of regulation to deal with the presence of symbiont but these mechanisms are still poorly understood. Here, we focused on the implication of lysozyme, a bactericidal enzyme, in this endosymbiosis. The relative expression of Ba-lysozymes paralogs and the global anti-microbial activity, were measured in natural population (Lucky Strike-1700m, Mid-Atlantic Ridge), and in in situ experimental conditions. B. azoricus individuals were moved away from the hydrothermal fluid to induce a loss of symbiont. Then after 6 days some mussels were brought back to the mussel bed to induce a re-acquisition of symbiotic bacteria. Results show the presence of 6 paralogs in B. azoricus. In absence of symbionts, 3 paralogs are up-regulated while others are not differentially expressed. Moreover the global activity of lysozyme is increasing with the loss of symbiont. All together these results suggest that lysozyme may play a crucial role in symbiont regulation

A Dynamic Model of the Proteins that Form the Initial Iron-Sulfur Cluster Biogenesis Machinery in Yeast Mitochondria

The final publication is available at link.springer.comThe assembly of iron-sulfur clusters (ISCs) in eukaryotes involves the protein Frataxin. Deficits in this protein have been associated with iron inside the mitochondria and impair ISC biogenesis as it is postulated to act as the iron donor for ISCs assembly in this organelle. A pronounced lack of Frataxin causes Friedreich’s Ataxia, which is a human neurodegenerative and hereditary disease mainly affecting the equilibrium, coordination, muscles and heart. Moreover, it is the most common autosomal recessive ataxia. High similarities between the human and yeast molecular mechanisms that involve Frataxin have been suggested making yeast a good model to study that process. In yeast, the protein complex that forms the central assembly platform for the initial step of ISC biogenesis is composed by yeast frataxin homolog, Nfs1–Isd11 and Isu. In general, it is commonly accepted that protein function involves interaction with other protein partners, but in this case not enough is known about the structure of the protein complex and, therefore, how it exactly functions. The objective of this work is to model the protein complex in order to gain insight into structural details that end up with its biological function. To achieve this goal several bioinformatics tools, modeling techniques and protein docking programs have been used. As a result, the structure of the protein complex and the dynamic behavior of its components, along with that of the iron and sulfur atoms required for the ISC assembly, have been modeled. This hypothesis will help to better understand the function and molecular properties of Frataxin as well as those of its ISC assembly protein partners.Postprint (published version

Iron-Sulfur Protein Assembly in Human Cells

Iron-sulfur (Fe-S) clusters serve as a fundamental inorganic constituent of living cells ranging from bacteria to human. The importance of Fe-S clusters is underscored by their requirement as a co-factor for the functioning of different enzymes and proteins. The biogenesis of Fe-S cluster is a highly coordinated process which requires specialized cellular machinery. Presently, understanding of Fe-S cluster biogenesis in human draws meticulous attention since defects in the biogenesis process result in development of multiple diseases with unresolved solutions. Mitochondrion is the major cellular compartment of Fe-S cluster biogenesis, although cytosolic biogenesis machinery has been reported in eukaryotes, including in human. The core biogenesis pathway comprises two steps. The process initiates with the assembly of Fe-S cluster on a platform scaffold protein in the presence of iron and sulfur donor proteins. Subsequent process is the transfer and maturation of the cluster to a bonafide target protein. Human Fe-S cluster biogenesis machinery comprises the mitochondrial iron-sulfur cluster (ISC) assembly and export system along with the cytosolic Fe-S cluster assembly (CIA) machinery. Impairment in the Fe-S cluster machinery components results in cellular dysfunction leading to various mitochondrial pathophysiological consequences. The current review highlights recent developments and understanding in the domain of Fe-S cluster assembly biology in higher eukaryotes, particularly in human cells