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

Olivieri, Paolo, Klabes, Moritz, Crack, Jason C., Lehmann, Angelika, Bennett, Sophie P., Le Brun, Nick E. ORCID: https://orcid.org/0000-0001-9780-4061 and Leimkuhler, Silke (2024) 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. ISSN 2165-0497

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Abstract

All sulfur transfer pathways generally have in common an l-cysteine desulfurase as the initial sulfur-mobilizing enzyme, which serves as a sulfur donor for the biosynthesis of numerous sulfur-containing biomolecules in the cell. In Escherichia coli, the housekeeping l-cysteine desulfurase IscS functions as a hub for sulfur transfer through interactions with several partner proteins, which bind at different sites on IscS. So far, the interaction sites of IscU, Fdx, CyaY, and IscX involved in iron sulfur (Fe-S) cluster assembly, TusA, required for molybdenum cofactor biosynthesis and mnm5s2U34 transfer RNA (tRNA) modifications, and ThiI, involved in both the biosynthesis of thiamine and s4U8 tRNA modifications, have been mapped. Previous studies have suggested that IscS partner proteins bind only one at a time, with the exception of Fe-S cluster assembly, which involves the formation of a ternary complex involving IscS, IscU, and one of CyaY, Fdx, or IscX. Here, we show that the affinity of TusA for IscS is similar to but lower than that of IscU and that these proteins compete for binding to IscS. We show that heterocomplexes involving the IscS dimer and single IscU and TusA molecules are readily formed and that binding of both TusA and IscU to IscS affects its l-cysteine desulfurase activity. A model is proposed in which the delivery of sulfur to different sulfur-requiring pathways is controlled by sulfur acceptor protein levels, IscS-binding affinities, and acceptor protein-modulated IscS desulfurase activity.

Item Type:	Article
Additional Information:	Funding information: This work was founded by the Deutsche Forschungsgemeinschaft (DFG) grant LE1171/11-2 and the DFG priority program SPP1927 grant LE1171/15-2 (to S.L.) and by the Biotechnology and Biological Sciences Research Council through grants BB/S001018/1, BB/T017708/1, BB/R013578/1 (to N.E.L.B.). Further support was provided by a British Mass Spectrometry Society Research Support Grant (to J.C.C.) and by UEA through the purchase/upgrade of the Bruker ESI-MS instrument. This article is based upon work from COST Action FeSImmChemNet, CA21115, supported by COST (European Cooperation in Science and Technology).
Faculty \ School:	Faculty of Science > School of Chemistry
UEA Research Groups:	Faculty of Science > Research Groups > Chemistry of Life Processes Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Depositing User:	LivePure Connector
Date Deposited:	02 Jul 2024 01:01
Last Modified:	13 Jul 2024 01:52
URI:	https://ueaeprints.uea.ac.uk/id/eprint/95728
DOI:	10.1128/spectrum.00949-24

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