Figure 8. Structural basis for catalytic promiscuity in SQOR.

A, Electrostatic surface potential map of the SQOR monomer, revealing a large electropositive cavity containing the exposed ³⁷⁹Cys-SSH persulfide, shown as a yellow sphere. GSH is docked in the cavity and shown as green spheres. B, Orientation of the docked GSH, shown as green sticks, relative to the active site cysteine persulfides, shown as pale green sticks with the persulfide sulfurs shown as yellow spheres. The thiol moiety of GSH is oriented proximal to ³⁷⁹Cys-SSH, which would facilitate sulfur transfer (PDB: 6OIB).