Maltose-binding protein (MBP) is a tool for protein expression and purification.

The expression and purification of recombinant proteins can in some cases be facilitated by the use of fusion protein technology. This approach entails the use of a highly soluble protein, well tolerated by the expression host, as a carrier molecule to which the protein of interest is fused, commonly on the carboxy-terminal side. Such a hybrid polypeptide is created by constructing a tail-to-head fusion of the genes encoding the carrier protein and the protein of interest, respectively, to form a single expression unit. In addition to facilitating the expression of problematic proteins in the host cell system, the carrier protein will also promote solubility and may confer a specific binding function enabling affinity-based purification of the hybrid molecule.

The maltose binding protein (MBP) of E. coli is a commonly used fusion partner which has been found particularly suitable for expression of allergens for diagnosic purposes, owing to it's low level of general background binding of specific IgE antibodies and very rarely occurring binding at a level above common background.
For users wishing to perform investigations at the highest possible level of stringency, an in vitro test carrying MBP alone is suitable as a negative control test.