Figure 1

Optimization of signal peptide and solubility tag leads to higher cytokine production and activity in the supernatant. (A) Different signal peptides were cloned upstream of the IL-2-His₆ gene. Bacterial supernatants were collected and IL-2 levels in the supernatant were measured using an IL-2 ELISA kit (indicated in red). Activity of IL-2 in the supernatants was measured using the CTLL-2 activity assay. RFUs normalized to non-expressing bacteria are shown (indicated in blue). (B) The InfB solubility tag was cloned to the N or C-terminus of the cytokine. Supernatants were collected and IL-2 signal was measured by ELISA (indicated in red). Activity of IL-2 in the supernatants was measured using a CTLL-2 activity assay. RFUs normalized to non-expressing bacteria are shown (indicated in blue). Values from three biological replicates with standard deviations are shown. *The LamB strain with C-terminal InfB tag was chosen for further experiments. RFU relative fluorescent unit, RBS ribosome binding site, Sig peptide signal peptide, His₆ hexahistidine tag.