Fusion expression of human pro-urokinase with E. coli thioredoxin

Human pro-urokinase (pro-UK) was cloned into plasmid pET32b and fused to the E. coli thioredoxin (trxA). When expressed in E. coli AD494(DE3), the fusion protein Trx-pro-UK accumulated as insoluble inclusion bodies and amounted to 35% of total cellular proteins. When co-expressed with molecular chaperones human protein disulfide isomerase (PDI) and E. coli GroESL, all the expressed products still existed in the form of insoluble inclusion bodies.