PUBEX/pUBSEX: a versatile expression vector system for production of fusion and nonfusion proteins in Escherichia coli

Abstract

Despite the large number of expression vectors now available, none provide the facility of allowing fusion and nonfusion protein production from the same vector system. In some situations it is preferable to obtain an insoluble fusion protein, in others a soluble nonfusion protein may be required. We have designed, constructed and tested a modification of the pEX vectors, in which it is possible to express the product of a suitably inserted cDNA either as part of a Cro-β-galactosidase (Cro-βGal) fusion or as a ΔCro fusion which contains only nine noninsert-encoded amino acids at its N terminus. The conversion from Cro-βGal to ΔCro fusion protein production is achieved by a simple intramolecular deletion of lacZ sequence from the pUBEX vector, to create the pUBSEX variant. Plasmid pUBEX can be induced to produce large amounts of insoluble Cro-βGal fusion proteins, whereas pUBSEX will produce predominantly soluble ΔCro fusion proteins.