The MBP tag or maltose binding protein tag is widely used in the expression and purification of recombinant proteins. It increases the solubility of proteins expressed in E. coli and the binding of MBP to amylose resin allows for affinity purification. The mature MBP protein expressed by E. coli is 370 amino acids in length with an approximate mass of 42.4 kilodaltons. Antibodies that target this protein can also be used in the immunological detection and analysis of proteins of interest that are MBP-tagged.