To determine the carbohydrate binding pocket of IPO, carbohydrates such as Me-Man, Me-Glc and Me-Gal were used to co-crystallize with the IPO protein. The crystals of IPOcarbohydrate complexes were determined in different space groups. IPO-Me-Man belongs to an orthorhombic space group C222 1 . The Matthew coefficient and solvent content for IPO-Me-Man had a reasonable value of 2.21 Å 3 /Da and 44.4% for 2 molecules in an asymmetric unit. Although only 2 IPO molecules were built in the IPO-Me-Man complex, the other 2 IPO molecules could be generated by symmetric operation (X, -Y, -Z) and resulted in a tetrameric association ( Figure 1B ). The crystal of IPO-Me-Glc was determined to be a monoclinic space group P2 1 . The Matthews coefficient and solvent content was 2.26 Å 3 /Da and 45.5% for 4 molecules. The packing results for IPO-Me-Man and IPO-Me-Glc indicated that the carbohydrates binding to IPO might result in a compact packing as compared with that of apo IPO. In addition, the resolved structure of IPO-Me-Glc formed a tetrameric association ( Figure 1C ).