We submitted the coordinates of a monomer of apo IPO (e.g., chain A; Figure S1C ) to the web service Matras for 3-D protein structure comparison [31] . We found the highest Z-score, 124.5, for the template structure, a dimeric form of Calsepa from Calydyrgia sepium (PDB: 1OUW; Figure S1D ) [27] , in our molecular replacement procedure. The following structures were PPL from Parkia platycephala with a hexahedral ring (PDB: 1ZGR; Figure  S1E ) [28] , Heltuba from Helianthus tuberosus with an octahedral ring Figure S1F ) [26] , Banlec from banana with an another kind of dimeric form (PDB: 2BMZ; Figure S1B ) [32] , and Jacalin from jackfruit seeds with a tetrameric form (PDB:1UGW; Figure S1A ) [33] . These data indicate the various quaternary structures in the JRL family, despite the same b-prism fold of protomer.