Changes in Protein Dynamics in Escherichia coli SufS Reveal a Possible Conserved Regulatory Mechanism in Type II Cysteine Desulfurase Systems

In the Suf Fe–S cluster assembly pathway, the activity of the cysteine desulfurase, SufS, is regulated by interactions with the accessory sulfotransferase protein, SufE. SufE has been shown to stimulate SufS activity, likely by inducing conformational changes in the SufS active site that promote the desulfurase step and by acting as an efficient persulfide acceptor in the transpersulfuration step. Previous results point toward an additional level of regulation through a “half-sites” mechanism that affects the stoichiometry and affinity for SufE as the dimeric SufS shifts between desulfurase and transpersulfuration activities. Investigation of the covalent persulfide intermediate of SufS by backbone amide hydrogen–deuterium exchange mass spectrometry identified two active site peptides (residues 225–236 and 356–366) and two peptides at the dimer interface of SufS (residues 88–100 and 243–255) that exhibit changes in deuterium uptake upon formation of the intermediate. Residues in these peptides are organiz...