Cooperative Effect of Multiple Domains in Copper Proteins Applied to H ₂ S Sensing

The revolutionary discovery by Abe & Kimura that H2S exerts a beneficial role in human body has renewed interest in this small molecule, long known for its toxicity. Understanding the (bio)reactivity of H2S with biological and bioinorganic targets is therefore of increasing importance, yet studies on its interaction with nonheme metalloproteins remain limited. Here, we investigate the reactivity of HS– with two natural multicopper proteins, SLAC and NiR. We demonstrate that SLAC, a two-domain blue-copper oxidase, can function as a multiwavelength, multireadout fluorescent sensor for H2S in complex environments. Comparative studies on NiR support the proposed mechanism of H2S recognition via selective reduction of copper centers. Finally, we benchmark the performance of these multicopper proteins against Cu-azurin, previously reported as a H2S recognition element, highlighting the advantages of multicopper architectures in terms of sensitivity, selectivity, and reversibility. Our findings establish multicopper proteins as versatile platforms for H2S sensing with potential applications in biomedical and environmental monitoring.