Maltose-binding protein (MBP) is a part of the maltose/maltodextrin system of Escherichia coli, which is responsible for the uptake and efficient catabolism of maltodextrins. MBP is used to increase the solubility of recombinant proteins expressed in E. coli. In these systems, the protein of interest is often expressed as a MBP-fusion protein, preventing aggregation of the protein of interest. In addition, MBP can itself be used as an affinity tag for purification of recombinant proteins. The fusion protein binds to amylose columns while all other proteins flow through. The MBP-protein fusion can be purified by eluting the column with maltose. Once the fusion protein is obtained in purified form, the protein of interest is often cleaved from MBP with a specific protease and can then be separated from MBP by affinity chromatography.