TusA is a versatile protein that links sulfur mobilization to iron homeostasis and translational efficiency in Escherichia coli
Final Report Abstract
Iron is important for many biological processes, including the TCA cycle, DNA biosynthesis, nitrogen fixation, electron transport and respiration. Due to both its essentiality and high reactivity, the intracellular iron concentration must be strictly regulated in the cell. In E. coli, the ferric uptake regulator (Fur) is mainly responsible to fine tune the iron homeostasis. Our studies show that the deletion of the tusA gene reduced and retarded the translation of the Fur protein, due to the lack of a specific tRNA thiolation controlling translation accuracy. This leads to iron accumulation in the cell and, together with a complex mis-regulation of transcription factors, small RNAs and modulators (as FNR, cAMP-CRP, ErpA, RyhB, FnrS, IscR, CyaY), this causes the reduction of Fe-S clusters assembled by the ISC and SUF systems. ISC and SUF systems are the two main Fe-S cluster assembly machineries in E. coli and both systems mobilise the sulfur through L-cysteine desulfurases, IscS and SufS respectively. While SUF system is limited to the production of Fe-S clusters mainly under oxidative stress and ironlimiting conditions, the ISC system is active under house-keeping and iron-rich conditions. The L-cysteine desulfurase IscS has a central role as sulfur donor for the biosynthesis of numerous sulfur-containing biomolecules by interacting with multiple partner proteins, which bind at different sites one at a time. In addition to TusA, IscS interacts with IscU, CyaY, Fdx and IscX, involved in iron sulfur (Fe-S) cluster assembly, or with ThiI, involved in the biosynthesis of thiamine and s4U8 tRNA modifications. The preference of IscS for a specific interaction partner determines consequentially the direction taken by the sulfur for the respective biosynthesis pathway. In our study we show that TusA is able to partially displace IscU from IscS thereby forming IscS-TusA-IscU heterocomplexes. In this heterocomplex, TusA affects the L-cysteine desulfurase activity of IscS and redirects the sulfur flow towards Moco biosynthesis and tRNA thiolation rather than Fe-S cluster assembly. Furthermore, TusA can completely displace CyaY from its complex with IscS. CyaY is the frataxin homolog of E. coli and its negative modulating effect on the formation of Fe-S cluster by ISC system has been extensively studied. In our work, the possibility if the displaced CyaY can interact with the second L-cysteine desulfurase SufS was investigated. The results indicate that CyaY is able to interact with SufS, alone or with the SufSE complex thereby drastically reducing its activity in vitro. The overexpression of CyaY in vivo has the effect of reducing the L-cysteine desulfurase activity of both IscS and SufS, under different growth conditions.
Publications
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The functional diversity of the prokaryotic sulfur carrier protein TusA. Advances in Microbial Physiology, 233-277.
Tanabe, Tomohisa Sebastian; Leimkühler, Silke & Dahl, Christiane
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TusA Is a Versatile Protein That Links Translation Efficiency to Cell Division in Escherichia coli. Journal of Bacteriology, 203(7).
Yildiz, Tugba & Leimkühler, Silke
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Eprenetapopt triggers ferroptosis, inhibits NFS1 cysteine desulfurase, and synergizes with serine and glycine dietary restriction. Science Advances, 8(37).
Fujihara, Kenji M.; Zhang, Bonnie Z.; Jackson, Thomas D.; Ogunkola, Moses O.; Nijagal, Brunda; Milne, Julia V.; Sallman, David A.; Ang, Ching-Seng; Nikolic, Iva; Kearney, Conor J.; Hogg, Simon J.; Cabalag, Carlos S.; Sutton, Vivien R.; Watt, Sally; Fujihara, Asuka T.; Trapani, Joseph A.; Simpson, Kaylene J.; Stojanovski, Diana; Leimkühler, Silke ... & Clemons, Nicholas J.
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Sulfur transferases in the pathways of molybdenum cofactor biosynthesis and tRNA thiolation in humans. Sulfurtransferases, 207-236.
Leimkühler, Silke & Ogunkola, Moses Olalekan
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The Human Mercaptopyruvate Sulfurtransferase TUM1 Is Involved in Moco Biosynthesis, Cytosolic tRNA Thiolation and Cellular Bioenergetics in Human Embryonic Kidney Cells. Biomolecules, 13(1), 144.
Ogunkola, Moses Olalekan; Guiraudie-Capraz, Gaelle; Feron, Francois & Leimkühler, Silke
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Binding of IscU and TusA to different but competing sites of IscS influences the activity of IscS and directs sulfur to the respective biomolecular synthesis pathway. Microbiology Spectrum, 12(8).
Olivieri, Paolo; Klabes, Moritz; Crack, Jason C.; Lehmann, Angelika; Bennett, Sophie P.; Le Brun, Nick E. & Leimkühler, Silke
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Shared functions of Fe-S cluster assembly and Moco biosynthesis. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1871(5), 119731.
Hasnat, Muhammad Abrar & Leimkühler, Silke
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TusA influences Fe-S cluster assembly and iron homeostasis in E. coli by reducing the translation efficiency of Fur. Microbiology Spectrum, 12(8).
Olivieri, Paolo; Zupok, Arkadiuz; Yildiz, Tugba; Oltmanns, Jonathan; Lehmann, Angelika; Sokolowska, Ewelina; Skirycz, Aleksandra; Schünemann, Volker & Leimkühler, Silke
