Production of recombinant human pancreatic secretory trypsin inhibitor by Escherichia coli

A synthetic gene for human pancreatic secretory trypsin inhibitor (PSTI) was fused to the coding sequence for the amino-terminal 135 amino acid residues of human interferon-gamma (IFN-gamma) by interposing a methionine codon sequence, and the resulting hybrid gene was efficiently expressed in Escherichia coli cells. Recombinant human PSTI (rHu-PSTI) was separated from the IFN-gamma/PSTI fused protein by cleavage at the methionine residue with cyanogen bromide. Finally, rHu-PSTI was purified by affinity chromatography on a bovine trypsin-CH-Sepharose 4B column. The amino acid composition, partial amino-terminal sequence, disulfide formation, human trypsin inhibitory activity, and immunoreactivity against rabbit anti-human PSTI serum of rHu-PSTI corresponded to those of the natural form.