A secretion expression system using promoter and signal peptide of cholera toxin B subunit gene.

A secretion expression plasmid vector pMC05S was constructed taking advantage of the promoter, signal peptide, and transcriptional terminator of cholera toxin B subunit gene and beta-galactosidase was overexpressed in E. coli and most of the expressed enzyme was secreted into periplasma when the lacZ gene was inserted downstream of the signal peptide sequence of pMC05S. The yield of beta-galactosidase by engineered E. coli reached 30 mg/L and most of the beta-galactosidase retained the activity of the enzyme. The appropriate host strain and medium were also investigated. This system provided a new approach for the expression of proteins that easily form inclusion bodies.