RESUMO
Frataxin is a ubiquitous protein that plays a role in Fe-S cluster biosynthesis and iron and heme metabolism, although its molecular functions are not entirely clear. In non-photosynthetic eukaryotes, frataxin is encoded by a single gene, and the protein localizes to mitochondria. Here we report the presence of two functional frataxin isoforms in Zea mays, ZmFH-1 and ZmFH-2. We confirmed our previous findings regarding plant frataxins: both proteins have dual localization in mitochondria and chloroplasts. Physiological, biochemical and biophysical studies show some differences in the expression pattern, protection against oxidants and in the aggregation state of both isoforms, suggesting that the two frataxin homologs would play similar but not identical roles in plant cell metabolism. In addition, two specific features of plant frataxins were evidenced: their ability to form dimers and their tendency to undergo conformational change under oxygen exposure.
Assuntos
Proteínas de Cloroplastos , Regulação da Expressão Gênica de Plantas/fisiologia , Proteínas de Ligação ao Ferro , Mitocôndrias , Proteínas Mitocondriais , Plastídeos , Zea mays , Proteínas de Cloroplastos/biossíntese , Proteínas de Cloroplastos/genética , Proteínas de Ligação ao Ferro/biossíntese , Proteínas de Ligação ao Ferro/genética , Mitocôndrias/genética , Mitocôndrias/metabolismo , Proteínas Mitocondriais/biossíntese , Proteínas Mitocondriais/genética , Plastídeos/genética , Plastídeos/metabolismo , Isoformas de Proteínas , Zea mays/genética , Zea mays/metabolismo , FrataxinaRESUMO
Nanocrystalline metals display interesting basic and technological properties related to their chemical and structural properties. Among other properties, they display a richer phase diagram due to the additional degree of freedom introduced by the nanoparticles surface. Metal nanoparticles encapsulated within biological macromolecules have the additional advantage of biocompatibility. In this paper we investigate the thermal evolution of the structure and dynamics of apoferritin encapsulated nanocrystalline copper. We determined the occurrence of a yet unexpected phase transition from a low temperature FCC to a complex high temperature phase including a (putative) amorphous precursor. The occurrence of a FCC-icosahedral transition is also discussed as a possible explanation to our results. The lattice dynamics of the FCC phase (monitored by its Debye temperature) differs from the behaviour expected for nanosized structures.