Zinc overload disrupts SoxR [2Fe–2S] clusters to drive redox-metallic crosstalk via SoxS-ZnuACB in Escherichia coli

Here, we demonstrate that excess zinc disrupts bacterial redox sensing by specifically disassembling the [2Fe-2S] cluster of SoxR - a master oxidative stress sensor in Escherichia coli. This impairment couples zinc overload to dysregulated oxidative defense, revealing a previously unrecognized metal-redox crosstalk mechanism. Using electron paramagnetic resonance (EPR) and UV-visible spectroscopy, we demonstrated that excess zinc specifically disrupts the assembly of the [2Fe-2S] cluster in redox-sensitive SoxR. Additionally, we assessed the expression levels of genes within this pathway using quantitative real-time PCR (qPCR) and quantified intracellular zinc and iron levels by inductively coupled plasma mass spectrometry (ICP-MS) to evaluate the roles of SoxS and the zinc uptake transporter ZnuACB in maintaining zinc homeostasis. Furthermore, we investigated the roles of SoxR, SoxS, and ZnuACB in bacterial zinc homeostasis through plate growth assays and gene knockout experiments. We establish that zinc excess disassembles SoxR [2Fe-2S] clusters as a molecular switch that dysregulates the SoxS-ZnuACB/SOD axis, converting zinc toxicity into oxidative vulnerability. This mechanistic insight exposes a bacterial Achilles' heel: targeting Fe-S cluster integrity disrupts redox-metal homeostasis, providing a strategy to combat antibiotic-resistant pathogens.