Biophysical Feature, Crystallization and X-ray Crystallographic Studies of Toxascaris leonina Galectin

Galectins are generally believed to be potential candidates for use in the development of novel anti-inflammatory agents or as selective modulators of the immune response. In particular, galectin-9 exhibits some of the extracellular functions, including cell aggregation, adhesion, chemoattraction, activation, and apoptosis. Tl-galectin (Tl-gal, galectin-9 homologue gene) was isolated from an adult worm of the Toxascaris leonina. The full-length Tl-gal gene, which was incorporated into pET-28a, was overexpressed in E. coli and purified by nickel affinity and gel filtration chromatographies. The purified Tl-gal was crystallized using the hanging-drop vapor-diffusion method. The crystal belonged to the tetragonal space group P4(1), with unit-cell parameters of a = b = 75.7 angstrom and c = 248.4 angstrom. The crystals were obtained at 20 degrees C and diffracted to a resolution of 3.0 angstrom. The asymmetric unit contained four molecules of Tl-gal, which gave a crystal volume per protein mass (Vm) of 2.8 angstrom(3) Da(-1) and a solvent content of 54.1%.