To further identify the role of the N terminus in the tetramerization of IPO, we prepared a truncated IPO (DN10IPO) by removing residues 1 to 10 to monitor the change in quaternary association. The native IPO protein or the truncated IPO protein was dissolved in the running buffer with 1 M glucose. Peak 1 in Figure 4B represents the native IPO, with molecular mass 63.2 kDa, which is a tetrameric size. Peak 2 in Figure 4B represents the DN10IPO, with molecular mass 21.9 kDa, which is near the truncated monomer size (16.3 kDa). The results further confirmed that IPO has a tetrameric association and its N terminus plays an important role in forming a tetramer.