An Escherichia coli vector to express and purify foreign proteins by fusion to and separation from maltose-binding protein

A plasmid vector has been constructed that directs the synthesis of high levels (approximately 2% of total cellular protein) of fusions between a target protein and maltose-binding protein (MBP) in Escherichia coli. The MBP domain is used to purify the fusion protein in a one step procedure by affinity chromatography to crosslinked amylose resin. The fusion protein contains the recognition sequence (Ile-Glu-Gly-Arg) for blood coagulation factor X a protease between the two domains. Cleavage by factor X a separates the two domains and the target protein domain can then be purified away from the MBP domain by repeating the affinity chromatography step. A prokaryotic (β-galactosidase) and a eukaryotic (paramyosin) protein have been successfully purified by this method.