Thiol peroxidase (Tpx) is an atypical 2‐Cys peroxiredoxin, which has been suggested to be important for cell survival and virulence in Gram‐negative pathogens. The structure of a catalytically inactive version of this protein in an orthorhombic crystal form has been
determined by molecular replacement. Structural alignments revealed that Tpx is conserved. Analysis of the crystal packing shows that the linker region of the affinity tag is important for formation of the crystal lattice.