Iron-sulfur (Fe-S) cluster assembly: the SufBCD complex is a new type of Fe-S scaffold with a flavin redox cofactor
Résumé
Assembly of iron-sulfur (Fe-S) clusters and maturation of Fe-S proteins in vivo require complex machineries. In Escherichia coli, under adverse stress conditions this process is achieved by the SUF system that contains six proteins: SufA, SufB, SufC, SufD, SufS and SufE. Here we provide a detailed characterization of the SufBCD complex whose function was so far unknown. Using biochemical and spectroscopic analyses we demonstrate that the complex (i) as isolated exists mainly in a 1:2:1 (B:C:D) stoichiometry, (ii) can assemble a [4Fe-4S] cluster in vitro and transfer it to target-proteins; and (iii) binds one molecule of a Flavin Adenine Dinucleotide per SufBC2D complex, only in its reduced form (FADH2), that has the ability to reduce ferric iron. These results suggest that the SufBC2D complex functions as a novel type of scaffold protein which assembles a Fe-S cluster through the mobilization of sulfur from the SufSE cysteine desulfurase and the FADH2-dependent reductive mobilization of Fe.
Domaines
Biochimie, Biologie Moléculaire
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