CONICET | Buscador de Institutos y Recursos Humanos

Fe-S clusters are among the oldest and mostversatile cofactors used by most living organisms. They are formed by atoms ofiron and inorganic sulfide. Although they can be synthesized non-enzymatically in vitro, their biosynthesis iscatalyzed by specific enzymes. Three complete systems responsible for thebiosynthesis of groups [Fe-S] were discovered in bacteria: NIF (nitrogen fixation),SUF (sulfur mobilization) and ISC (iron and sulfur cluster) and in eukaryotesthe presence of a ISC and SUF homologous system in mitochondria andchloroplasts, respectively. In this work we address the initialcharacterization of this pathway in algae. First, we performed theidentification in silico of gene andprotein sequences possibly related to the biogenesis of Fe-S clusters in greenand brown algae (Nannochloropsis gaditana, Chlorella vulgaris and Ectocarpussiliculosus) using the Phytozome database (https://phytozome.jgi.doe.gov).After performing sequence alignments and considering the high conservation foundbetween the amino acid sequences, the frataxin from N. gaditana (NangaFH)was selected to perform its functional characterization. The sequence ofNangaFH contains 204 amino acids, a mitochondrial targeting transit peptide of82 residues and a frataxin domain comprised[MVB1] between residues 94 to 199. Withinthis domain the iron-binding sites are conserved (E95, D103, E104, D107, A111,D114, A115, D122 and E124). The recombinant protein was expressed in E. colicells and purified to homogeneity. We evaluated their ability of NangaFH toattenuate the Fenton reaction by measuring the inhibition of malondialdehydeproduction after the addition of thiobarbituric acid. As previously suggested,frataxin could function as iron chaperone and in this way, its presence couldattenuate oxidative damage by metals. Results showed that NangaFH did not attenuatedthe Fenton reaction in contrast to the frataxins from C. vulgaris and A.thaliana(both proteins atennuated the fenton reaction about 23%). To determine whether NangaFHoverexpression decreases the sensitivity of E.coli cells to oxidative and metal stress, bacterial cells overexpressingthis protein were incubated in the presence of hydrogen peroxide, cromium and zinc.Our results showed that the expression of NangaFH allowed a better growth of E.coli cells under oxidative conditions. These results suggest that algae frataxinwould have a protective role against oxidative stress in algae. [MVB1]Dicha secuencia contiene 204 aminoácidos, un péptido tránsito dedireccionamiento mitocondrial de 82 residuos y un dominio frataxina comprendidoentre los residuos 94 y 199. Dentro de este dominio los sitios de unión ahierro se encuentran conservados (E95, D103, E104, D107, A111, D114, A115, D122y E124).

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