Structural Evidence for Dimer-Interface-Driven Regulation of the Type II Cysteine Desulfurase, SufS

SufS is a type II cysteine desulfurase and acts as the initial step in the Suf Fe–S cluster assembly pathway. In Escherichia coli, this pathway is utilized under conditions of oxidative stress and is resistant to reactive oxygen species. Mechanistically, this means SufS must shift between protecting a covalent persulfide intermediate and making it available for transfer to the next protein partner in the pathway, SufE. Here, we report five X-ray crystal structures of SufS including a new structure of SufS containing an inward-facing persulfide intermediate on C364. Additional structures of SufS variants with substitutions at the dimer interface show changes in dimer geometry and suggest a conserved β-hairpin structure plays a role in mediating interactions with SufE. These new structures, along with previous HDX-MS and biochemical data, identify an interaction network capable of communication between active-sites of the SufS dimer coordinating the shift between desulfurase and transpersulfurase activities