Maturation of Fe-S proteins in plant organelles.
Résumé
Iron is an essential microelement because numerous metabolic processes and electron transfer reactions rely on heme- and iron-sulfur (Fe-S)-containing proteins. Plants possess three machineries dedicated to the maturation of Fe-S proteins, namely SUF, ISC, and CIA, present in plastids, mitochondria and in the cytosol/nucleus, respectively. The assembly process can be split into two major steps, (i) the de novo assembly on scaffold proteins, that requires ATP, iron and sulfur atoms, electrons and thus the concerted action of several proteins forming ‘early-acting’ assembly complexes, and (ii) the conversion and transfer of the preformed Fe-S cluster to client proteins using a set of ‘late-acting’ maturation factors. The function of the mitochondrial and chloroplastic sets of maturation factors was analyzed by combining several approaches i.e., complementation of yeast mutants, molecular and physiological studies of A. thaliana insertion mutants even though many of them are essential for embryo development but also biochemical and spectroscopic characterization of recombinant proteins. In addition, direct interaction partners were identified by binary yeast two-hybrid experiments and/or pull-down experiments and their capacity to exchange Fe-S clusters verified. Our data allowed delineating some interconnections among SUF and ISC components and the maturation pathways of specific Fe-S proteins present in organelles.