Construction of a chimeric intein-containing protein and the search for conditions for its cleavage

Protein splicing is a post-translational autocatalytic process that results in the excision of an internal peptide (the intein) from a precursor protein and the ligation of the flanking protein sequences (the exteins). The high specificity of intein-mediated excision of protein precursors permits the use of protein splicing in biotechnology. This work was aimed the production of human growth hormone with a native N-terminus in E. coli. A chimeric protein consisting of a short N-terminal peptide, the Mxe GyrA intein, and human growth hormone was constructed. The formyl-methionine modified N-terminal peptide was intended for removal via splicing during translation. This intein has been shown to mediate the cleavage of exteins, but their subsequent ligation has never been observed. This permitted the production of human growth hormone with the native N-terminus. The effect of various factors on cleavage efficiency was also studied. The most efficient cleavage of the chimeric protein (60–80%) was observed in the presence of an inductor (100 mM β-mercaptoethanol) upon incubation for 4–6 days.