Structure of insect-cell-derived IL-22

The crystal structure of interleukin-22 expressed in Dros­ophila melanogaster S2 cells (IL-22_Dm) has been determined at 2.6 Å resolution. IL-22_Dm crystals contain six molecules in the asymmetric unit. Comparison of IL-22_Dm and IL-22_Ec (interleukin-22 produced in Escherichia coli) structures reveals that N-linked glycosylation causes only minor structural changes to the cytokine. However, 1–4 Å main-chain differences are observed between the six IL-22_Dm monomers at regions corresponding to the IL-22R1 and IL-­10R2 binding sites. The structure of the carbohydrate and the conformational variation of IL22_Dm provide new insights into IL-22 receptor recognition.