TusA is a versatile protein that links sulfur mobilization to iron homeostasis and translational efficiency in Escherichia coli

• Applicant: Professorin Dr. Silke Leimkühler
• Subject Area: Biochemistry
• Term: from 2014 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262101759

Sulfur is an essential element for all living organisms. In Escherichia coli, the sulfur is mobilized by IscS from L-cysteine in form of a protein-bound persulfide that is utilized as the universal sulfur-donor for the biosynthesis of iron-sulfur clusters, thiamine, biotin, lipoic acid, the molybdenum cofactor (Moco), and several thiolated nucleosides present in certain tRNAs. To accomplish these cellular roles, IscS interacts with numerous proteins. One of the interaction partners of IscS is the TusA protein, for which a dual cellular role has been described so far, since TusA is involved as sulfur transferase in molybdenum cofactor biosynthesis and in the formation of mnm5s2U34 modified nucleosides at position 34 in tRNA. However, previous studies showed that a deletion of tusA causes a pleiotropic effect on even more cellular pathways in E. coli, not only including tRNA thiolation and Moco biosynthesis, but also on the enhanced susceptibility of viral infection inhibition by programmed ribosomal frameshifting in addition to a filamentous growth phenotype. Additionally, a tusA deletion strain accumulates ferrous iron and has a reduced iron-sulfur cluster content. Overall, this emphasizes that TusA has a pleiotropic cellular role. The initial results point to a regulatory role of TusA on the activity of IscS by coordinating the iron and sulfur entry to the protein interaction network centered around IscS.In the next funding period we want to study the role of TusA for Fe-S cluster assembly and tRNA thiolations in further detail. We will investigate the role of TusA on the activity of the IscS/IscU/CyaY complex. Further, the role of TusA in cellular Fe2+ accumulation and ROS production will be investigated. Initial studies pointed to a role of TusA in cell division by having a role on the translational efficiency of proteins involved in these processes. Overall, we plan to investigate the multiple phenotypes of a tusA deletion strain and will shed light on remaining mysteries of the role of this versatile protein in E. coli.

• DFG Programme: Research Grants