Maltose binding protein (MBP) encoded by the malE gene in Escherichia coli, is a 44-kD monomeric periplasmic protein. MBP is component of the Escherichia coli maltose/maltodextrin system, which regulates the uptake and catabolism of maltrodextrins as part of the chemotactic response. This protein is used in recombinant protein expression as an affinity and solubility tag. Glutathione S Transferase Alpha 3 (GSTa3) has been identified as an interactor of MBP, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant MBP and recombinant mouse GSTa3. Briefly, biotin-linked MBP were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to GSTa3-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µl stop solution to the wells and read at 450 nm immediately. The binding activity of recombinant MBP and recombinant mouse GSTa3 was shown in Figure 1, the EC50 for this effect is 0.46 ug/mL.