Figure 1.

CsoR family repressor tetramer architecture and a cartoon representation of asymmetric crosslinked species. (A) Representation of a generic CsoR-family tetramer (each protomer shaded differently) with the WXYZ motif site shown. (B) SpCstR dimer of dimers architecture with each cysteine thiol represented by an S (right). S³⁰ and S⁵⁹ represent the thiolate sulfurs of residues Cys30 and Cys59, respectively, that correspond to C31 and C60 in SaCstR. (C) Representation of the different oxidation states that can be captured in a mass spectrometry-based kinetic profiling experiment with each cysteine thiol represented by an S. Red line, covalent crosslink of some kind (either di-, tri- or tetrasulfide bond) between Cys residues on opposite protomers, resolvable by ESI-MS. A more schematic representation of SpCstR or SmCstR (one-half of the tetramer) and used in Figures 7 and 8 is shown in the bottom, with the Cys residues indicated in boxes.