The vector pMAL-c5E is designed to produce maltose-binding protein (MBP) fusions, where the protein of interest can be cleaved from MBP with the specific protease Enterokinase (NEB #P8070). MBP fusions made with this vector are expressed cytoplasmically. The MBP has been engineered for tighter binding to amylose resin. A gene or open reading frame is inserted into a restriction site of the vector polylinker, in the same translational reading frame as themalEgene (encoding MBP). The fusion protein produced from the vector can be purified by amylose affinity chromatography. The sequence coding for the five amino acids Asp-Asp-Asp-Asp-Lys is present just upstream of the KpnI site. This allows the protein of interest to be cleaved from maltose-binding protein with enterokinase.