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<p>Iron-sulfur clusters are versatile protein cofactors involved in diverse biological processes, but their role in hydrogen sulfide/hydrosulfide (H<sub>2</sub>S/HS<sup>-</sup>) sensing remains largely unexplored. Here, we report that the <i>Bacillus licheniformis</i> 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 O<sub>2</sub>, correlating with increased NreB kinase activity. Electron paramagnetic resonance spectroscopy shows that the cluster retains its oxidized [2Fe-2S]<sup>2+</sup> state during sulfide-sensing. Molecular dynamics simulations further reveal transient solvent and HS<sup>-</sup> 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.</p>

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A labile sulfur ligand in a three-cysteine-coordinated [2Fe−2S] cluster mediates sulfide sensing in NreB

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月30日

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  • Chao Tang,
  • Yuemeng Shen,
  • Jingyao Qu,
  • Lu Yu,
  • Honglei Liu,
  • Huaiwei Liu,
  • Luying Xun,
  • Yongzhen Xia

摘要

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.