Fig. 3

Biochemical characterization of denatured and soluble recombinant proteins. The cell lysates of recombinant cultures induced with different IPTG concentrations were resolved on 16 and 14% SDS‒PAGE to assess the expression of HCV-core (A, C) and E1/E2 (B, D), respectively. Multiple protein bands were visualized in both insoluble protein profiles, where prominent bands of core protein were detected at molecular weights range ~ 30–45 kDa, whereas E1/E2 was visualized as a dominant band at ~ 90kDa with minor bands at lower M. wts (red arrow heads). The inclusion of glycylglycine improved the solubility of recombinant core and E1/E2, where both were visualized at the expected M. wt. of ~ 21 (black arrowheads) and 61 kDa (red arrowheads), respectively compared with the glycylglycine-free cultures (lane C). The protein profiles showed that 0.4 and 0.1M final concentration of glycylglycine produced the highest yield of soluble core and E1/E2, respectively, while higher concentrations produced a lower M.wt. protein forms (black and red arrows, respectively), and therefore they were used for protein purification (lane P).The integration of glycylglycine in the culture media also enhanced the cell density (E) and purified protein yield (F) in a concentration-dependent manner