The expression of IRED10, IRED15, IRED20, IRED23 and AspRedAm was performed on the basis of a previously described protocol. The proteins were expressed in E. coli BL21(DE3) strains containing pET22-or pET28-based plasmids with the genes of IREDs or AspRedAm. Cultures were grown at 37 °C (180 rpm) in 1 L lysogeny broth (LB) containing 100 µg/mL ampicillin or 50 µg/mL kanamycin. Prior to induction at an OD600 of 0.6, the culture was cooled to 20 °C. After induction with 0.2 mM isopropyl β-D-1thiogalactopyranoside the culture was further incubated overnight (20 hours) at 20 °C. After harvesting, the proteins were lysed by sonication and purified using the His-tag. The elution buber (50 mM sodium phosphate, 300 mM sodium chloride, 250 mM imidazole, pH 8.0) was replaced with a storage buber (50 mM sodium phosphate with 300 mM sodium chloride, 10 % glycerol, pH 8.0) using PD-10 desalting columns (GE Healthcare, UK).