RESUMO
Recent studies in bacteria and eukaryotes have led to the identification of several new genes implicated in the biogenesis of iron-sulfur (Fe/S) cluster-containing proteins. This report focuses on two genes of bakers yeast Saccharomyces cerevisiae, ISU1 and ISU2, which encode homologues to bacterial IscU and NifU, potential iron-binding or cluster-assembly proteins. As with other yeast genes implicated in Fe/S protein assembly, deletion of either ISU1 or ISU2 results in increased accumulation of iron within the mitochondria, loss of activity of the [4Fe-4S] aconitase enzyme, and suppression of oxidative damage in cells lacking cytosolic copper/zinc superoxide dismutase. Both genes are induced in strains expressing an activated allele of Aft1p, the iron-sensing transcription factor, suggesting that they are regulated by the iron status of the cell. Immunoblotting studies using an antibody directed against Escherichia coli IscU reveal that both Isu1p and Isu2p are localized primarily in the mitochondria and that Isu1p is the predominant form expressed under all growth conditions tested. The possible role of the Isu proteins in the assembly and/or repair of Fe/S clusters is discussed.
Assuntos
Proteínas Fúngicas/genética , Genes Fúngicos , Família Multigênica , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Sequência de Aminoácidos , Azotobacter vinelandii/genética , Proteínas de Bactérias/genética , Sequência de Bases , Sequência Conservada , Cisteína/genética , DNA Fúngico/genética , Proteínas Fúngicas/metabolismo , Expressão Gênica , Ferro/metabolismo , Proteínas Mitocondriais , Dados de Sequência Molecular , Mutação , RNA Mensageiro/genética , Saccharomyces cerevisiae/metabolismo , Homologia de Sequência de AminoácidosRESUMO
Archaeoglobus fulgidus is the first sulphur-metabolizing organism to have its genome sequence determined. Its genome of 2,178,400 base pairs contains 2,436 open reading frames (ORFs). The information processing systems and the biosynthetic pathways for essential components (nucleotides, amino acids and cofactors) have extensive correlation with their counterparts in the archaeon Methanococcus jannaschii. The genomes of these two Archaea indicate dramatic differences in the way these organisms sense their environment, perform regulatory and transport functions, and gain energy. In contrast to M. jannaschii, A. fulgidus has fewer restriction-modification systems, and none of its genes appears to contain inteins. A quarter (651 ORFs) of the A. fulgidus genome encodes functionally uncharacterized yet conserved proteins, two-thirds of which are shared with M. jannaschii (428 ORFs). Another quarter of the genome encodes new proteins indicating substantial archaeal gene diversity.
