Effects of the chaperone co-expression on the yields of soluble target proteins. (a) Coomassie-stained SDS-PAGE showing target proteins purified by metal affinity chromatography either from control cells (C; without chaperone overexpression) or from different host cells overexpressing chaperone combinations 1 to 5 (indicated by the numbers above the lanes). The proteins Oskar3, Susy, and E8R2 were purified from cells grown with the one-step protocol. (b) Chaperone over-expression (combination 5) in host cells prevents the co-elution of the target protein E8R1 together with GroEL. (c) Comparison of the TEV activity using TEV protease purified from wild type cells and chaperone over-expressing cells (combination 3). (d) CD analysis of the TEV protein purified from wild type cells without (gray line) and with chaperone overexpression (combination 3, black line).