Cluster occupancy- and oxidation state-dependence of Yersinia enterocolitica IscR DNA binding

Gray, Elizabeth, Gao, Miaomiao, Bradley, Justin, Crack, Jason C. and Le Brun, Nick E. (2025) Cluster occupancy- and oxidation state-dependence of Yersinia enterocolitica IscR DNA binding. Journal of Inorganic Biochemistry. ISSN 0162-0134

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Abstract

Iron‑sulfur (Fesingle bondS) clusters are protein cofactors essential for life. Their assembly requires dedicated cellular machineries, such as the ISC system, found in Escherichia coli and many other bacteria. ISC is regulated by IscR, a member of the Rrf2 family of transcriptional regulators. E. coli IscR (EcIscR) binds a [2Fesingle bond2S] cluster and, in this form, functions as a repressor of the isc operon. Under aerobic conditions there is an increased cellular demand for Fesingle bondS clusters, and apo IscR accumulates resulting in upregulation of ISC. Currently, the signal that EcIscR directly responds to is not clear. Little is known about other IscR homologs and whether key functional features of the E. coli protein are broadly shared. Here, we report studies of the IscR homolog from the pathogen Yersinia enterocolitica. Y. enterocolitica IscR (YeIscR) is ~80 % identical to EcIscR and binds a [2Fesingle bond2S] cluster most likely coordinated by three conserved Cys residues and one His. Isolated in the 1+ oxidation state, exposure to O2 or other oxidants resulted in rapid oxidation of the cluster to the +2 state and slow cluster loss. The cluster was relatively insensitive to iron chelators, indicating that it is not labile. While the trigger for degradation of the YeIscR cluster to generate the apo form is not clear, loss of the cluster resulted in a ~10-fold decrease in DNA affinity. The oxidation state of the cluster was found to be important for DNA binding, with a significant reduction in IscR-bound DNA observed upon oxidation, suggesting possible physiological importance.

Item Type:	Article
Additional Information:	Data Availability: Data supporting the conclusions of this study are available in the main paper with additional experimental data given in the Supplementary Data. All data are available from the corresponding author upon request. Funding: This work was supported by the award of a Biotechnology and Biological Sciences Research Council Norwich Research Park Doctoral Training Partnership PhD studentship to EG, BBSRC grant BB/V006851/1 and the Royal Society International Exchange grant IEC\R2\170168. BBSRC grant BB/R013578/1 supported the purchase of an ICP-QQQ-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 (former - to 2024) Faculty of Science Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
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:	23 Jul 2025 11:30
Last Modified:	23 Jul 2025 11:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99978
DOI:	10.1016/j.jinorgbio.2025.113011

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