Manual model rebuilding involved use of Coot [40] , alternating refinement by the CNS program, with 5% or 10% of the observed reflections randomly selected and set aside for calculation of the R free value. The final refined statistics are in Table 3 . For the protein interface of the tetrameric form, IPO-Me-Glc was used as a representative for analysis by the web service PDBe PISA [34] . All molecular representations were prepared with use of Deep-View [41] and PyMOL [42] . The coordinates of monomers of apo IPO (e.g., chain A) were subjected to the web service Matras for structure comparison [31] . 