The apo IPO showed an orthorhombic space group of I222. A reasonable volume of the unit cell (Vm) for the Matthew coefficient was estimated at 2.19 Å 3 /Da and 44% solvent content by 8 IPO molecules. However, only 5 IPO molecules in an asymmetric unit could be built after molecular replacement. We structure. The carbohydrates Me-Man, Me-Glc, and Me-Gal share 9 hydrogen-bonding interactions with Gly21, Tyr97, Gly141, Trp142, Tyr143 and Asp145 of IPO (blue triangle). The residues of IPO located at the interface are boxed in red. The two short b strands at the N terminus are also involved in the interface. The underlined Jacalin-tetramer representing the sequence is extracted from the C terminus of Jacalin (chain B). doi:10.1371/journal.pone.0040618.g002 obtained a higher Matthew coefficient with 3.51 Å 3 /Da and 65% solvent content. In the packing diagram for apo IPO, we observed a tetrameric association with an additional monomer in an asymmetric unit ( Figure 1A ). The additional monomer could form a tetrameric association with the other 3 neighboring molecules, which were generated by symmetric operations (-X, Y, -Z), (X, -Y, -Z), and (-X-1, -Y, Z). So 4 IPO molecules could form a tetramer.