Purification, crystallization and preliminary crystallographic studies of the complex of interferon‐λ1 with its receptor

Human interferon‐λ1 (IFN‐λ1 Ins ) and the extracellular domain of interferon‐λ1 receptor (IFN‐λ1R1) were expressed in Drosophila S2 cells and purified to homogeneity. Both IFN‐λ1 Ins and interferon‐λ1 produced from Escherichia coli (IFN‐λ1 Bac ) were coupled with IFN‐λ1R1 at room temperature and the complexes were purified by gel filtration. Both complexes were crystallized; the crystals were flash‐frozen at 100 K and diffraction data were collected to 2.16 and 2.1 Å, respectively. Although the IFN‐λ1 Bac –IFN‐λ1R1 and IFN‐λ1 Ins –IFN‐λ1R1 complexes differed only in the nature of the expression system used for the ligand, their crystallization conditions and crystal forms were quite different. A search for heavy‐atom derivatives as well as molecular‐replacement trials are in progress.