Fig. 1

Construction of expression vectors. a The first expression vector pET-P-Intein-ELK16 was based on the previously constructed vector pET30a-LipA-I-ELK16. The second vector pET-Trx-P-Intein-ELK16 was derived from the first vector by inserting the thioredoxin (Trx) sequence followed by an enterokinase cleavage site Asp–Asp-Asp–Asp–Lys (D₄K) upstream of the target peptide. b Schematic for producing recombinant peptides using vector pET-Trx-P-Intein-ELK16. c Expression and intein-mediated cleavage result of Trx. Lane IL, insoluble fraction of cell lysate after washing twice with buffer B1; lanes IC and SC, insoluble and soluble fraction of cleaved fusion protein