TusA influences Fe-S cluster assembly and iron homeostasis in by reducing the translation efficiency of Fur.

All sulfur transfer pathways have generally a l-cysteine desulfurase as an initial sulfur-mobilizing enzyme in common, which serves as a sulfur donor for the biosynthesis of numerous sulfur-containing biomolecules in the cell. In , the housekeeping l-cysteine desulfurase IscS has several interaction partners, which bind at different sites of the protein. So far, the interaction sites of IscU, Fdx, CyaY, and IscX involved in iron-sulfur (Fe-S) cluster assembly have been mapped, in addition to TusA, which is required for molybdenum cofactor biosynthesis and mnmsU34 tRNA modifications, and ThiI, which is involved in thiamine biosynthesis and sU8 tRNA modifications. Previous studies predicted that the sulfur acceptor proteins bind to IscS one at a time. TusA has, however, been suggested to be involved in Fe-S cluster assembly, as fewer Fe-S clusters were detected in a mutant. The basis for this reduction in Fe-S cluster content is unknown. In this work, we investigated the role of TusA in iron-sulfur cluster assembly and iron homeostasis. We show that the absence of TusA reduces the translation of , thereby leading to pleiotropic cellular effects, which we dissect in detail in this study.IMPORTANCEIron-sulfur clusters are evolutionarily ancient prosthetic groups. The ferric uptake regulator plays a major role in controlling the expression of iron homeostasis genes in bacteria. We show that a mutant is impaired in the assembly of Fe-S clusters and accumulates iron. TusA, therefore, reduces mRNA translation leading to pleiotropic cellular effects.