The pTZ18UH-IPO and pTZ18UH-DN10IPO vectors were transformed into Escherichia coli BL21 (DE3) cells (Novagen). A single colony was cultured in 5 ml LB medium containing 100 mg/ ml ampicillin (LB/Amp) at 37uC overnight. The medium was further transferred into 600 ml LB/Amp to an A 600 of about 0.5 to 0.7 and then induced with 0.1 mM isopropyl-b-D-thiogalactopyranoside (IPTG) at 25uC for 6 hr. Cells harvested by centrifugation were resuspended in a loading buffer (20 mM sodium phosphate, pH 7.4, 0.5 M sodium chloride, 20 mM imidazole). After breaking cells by use of an ultrasonicator (Sonicator 3000, Misonix), the supernatant of the crude cell lysate was loaded onto a Histrap FF column (GE Healthcare) with use of an Ä kta Prime fast protein liquid chromatography (FPLC) system (GE Healthcare). After washing the Histrap FF column with 3x column volume of loading buffer (1x phosphate buffered saline, 5 mM adenosine triphosphate, 10 mM MgSO 4 ), the IPO protein was eluted by use of elution buffer (50 mM sodium phosphate, pH 7.4, Table 3 . Crystallography statistics for apo ipomoelin (IPO) and IPO in complex with carbohydrates methyl a-D-mannopyranoside (Me-Man), methyl a-D-glucopyranoside (Me-Glc) and methyl a-D-galactopyranoside (Me-Gal). sodium formate, 40% w/v polyethylene glycol 3,350. The crystals of IPO-Me-Gal appeared in 7 days. A mixture of the reservoir solution with 100% glycerol in a 4:1 volume ratio was used as cryo-protectant for data collection. The diffraction data were collected at 100K and detected by a Quantum 315 or Quantum 210 CCD detector at the BL13B1 or BL13C1 beamlines of NSRRC (Hsinchu, Taiwan). All diffraction data were processed and scaled with use of the HKL2000 program [38] . The diffraction statistics are in Table 3 .