Crystals of Bj-xtrIT-(His6) diffracted to 1.7 Å resolution (Table 1) and were solved by molecular replacement using the previously-reported Bj-xtrIT structure [11]. Recombinant Bj-xtrIT-(His6) has both the βαββα-fold and C1–C4, C2–C6, C3–C7, and C5–C8 disulfide connectivity of the native fold (Fig. 1 and Fig. 5A). An all-atom structural superimposition of Bj-xtrIT-(His6) with the untagged Bj-xtrIT structure [11] (Fig. 5B) shows that there is a root-mean-square deviation (RMSD) of 0.45 Å. The structures differ only in side-chain rotamers for some residues located on the surface of the toxin, reflecting the difference in crystal contacts that the toxin forms under different crystal packing conditions (space groups C2221 vs I4122). Nevertheless the backbone atoms and disulfide groups all superimpose and show that recombinant Bj-xtrIT-(His6) was expressed with the native conformation.