eLife assessment
This study presents findings on the structure and dynamics of the Type I ABC importer and bacterial osmolarity regulator OpuA, addressing the question of whether the substrate binding domains physically interact in a salt-dependent manner. Based on a collective assessment of the single-molecule fluorescence resonance energy transfer and cryogenic electron microscopy data, the researchers convincingly conclude that the substrate domains directly interact. These findings are valuable and it will be interesting to see if future studies can provide further evidence of this direct interaction and define it in further detail.