Abstract
Iron-sulfur clusters are versatile protein cofactors involved in diverse biological processes, but their role in hydrogen sulfide/hydrosulfide (H2S/HS-) sensing remains largely unexplored. Here, we report that the Bacillus licheniformis sensor kinase NreB contains an unusual [2Fe-2S] cluster within its PAS domain. A 1.52-Å crystal structure reveals a distinct coordination geometry where three conserved cysteine residues and a non-cysteinyl sulfur ligand stabilize the cluster. Biochemical and native mass spectrometry support assignment of the predominant ligand state as -SH and show enrichment of -SSH/SSOH-like state upon sulfide exposure in the presence of O2, correlating with increased NreB kinase activity. Electron paramagnetic resonance spectroscopy shows that the cluster retains its oxidized [2Fe-2S]2+ state during sulfide-sensing. Molecular dynamics simulations further reveal transient solvent and HS- accessibility to the buried cluster, providing a physical basis for ligand entry. Here, we show that bacteria sense sulfide via a three-cysteine-coordinated Fe-S cluster with a labile sulfur ligand.
Acknowledgements
We thank the staff members of the Electron Spin Resonance System (https://cstr.cn/31125.02.SHMFF.ESR) at the Steady High Magnetic Field Facility, CAS (https://cstr.cn/31125.02.SHMFF). We thank Prof. Xiang Gao and Pixian Gong from Shandong University for advice on the Western blot experiments. We also thank Guannan Lin and Jing Zhu of the Core Facilities for Life and Environmental Sciences, State Key laboratory of Microbial Technology of Shandong University for LC-MS and DLS analyses.
Funding
This work was supported by grants from the National Natural Science Foundation of China (Grant No. 32370037 to Y.Z.X and 92351302 to L.Y.X.) and the Shandong Provincial Natural Science Foundation (Grant No. ZR2023MC004 to Y.Z.X.). Additional funding was provided through the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2022455 to L.Y.), and the Intramural Joint Program Fund of the State Key Laboratory of Microbial Technology (Project No. SKLMTIJP-2024-10 to Y.Z.X.). All other authors declare no relevant funding.
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Tang, C., Shen, Y., Qu, J. et al. A labile sulfur ligand in a three-cysteine-coordinated [2Fe−2S] cluster mediates sulfide sensing in NreB. Nat Commun (2026). https://doi.org/10.1038/s41467-026-73842-2
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DOI: https://doi.org/10.1038/s41467-026-73842-2
