Modulation of expression of the human gamma interferon gene in E.coli by site-directed mutagenesis

Abstract Plasmids expressing 2 forms of human immune interferon (IFN-γ) in E. coli have been constructed: 1) pIFNTacI which expresses IFN-γ with an N-terminal amino acid sequence of met-cys-tyr-cys-gln-, and 2) pIFNTacII which is a derivative of pIFNTacI from which the 9 base pairs (bp) coding for the cys-tyr-cys have been deleted. Quantitation of Western blots showed that approximately 10-fold more IFN-γ was produced in cells harboring pIFNTacII (7.5% of total cellular protein) as compared to pIFNTacI. The IFN-γ expressed in E. coli pIFNTacII is biologically active and routinely recoverable at 10 9 units per liter. When examined microscopically, IPTG induced E. coli harboring either plasmid construction contains prominent cytoplasmic inclusion bodies.