This ProteomeXchange dataset contains native mass spectrometry and intact-protein mass spectrometry data generated in support of the manuscript “A labile sulfur ligand in a three-cysteine-coordinated [2Fe-2S] cluster mediates sulfide sensing in NreB”. The dataset includes intact-protein MS measurements of purified His_NreB and His_NreB_PAS for molecular-mass verification, as well as native MS measurements of NreB_PAS under untreated, GSH-treated, GSH plus NaHS-treated, and pH-dependent conditions. These data were used to characterize Fe-S cluster-associated adduct states and to compare the distributions of species detected under different conditions. Raw data acquired on a Bruker Impact HD mass spectrometer and the corresponding deconvolution outputs generated using Bruker DataAnalysis 4.2 are included together with a deconvolution summary table.