Figure 4: The effects of IPTG concentrations (mM) and incubation temperature on Trx-EpEX fusion protein expression in Escherichia coli OrigamiTM (DE3). After separation on a 12 % SDS-PAGE gel, protein bands were visualized by coomassie brilliant blue R250 staining. Protein expression was induced with different concentration of IPTG (0.25, 0.5, 1 or 2 mM) at (A) 16 °C, (B) 25 °C, (C) 30 °C, and (D) 37 °C for 5 h. Lane M, protein marker; lane U, bacterial culture before induction. The arrows indicate the position of Trx-EpEX. EpEX, Epithelial extracellular domain; Trx, thioredoxin; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; IPTG, isopropyl-β-d-thiogalactopyranoside.