Purification and crystallization of yeast glycosylphosphatidylinositol transamidase subunit PIG-S (PIG-S_71–467)

The PIG-S_71–467 subunit of the yeast GPI transamidase complex was cloned, overexpressed, purified and crystallized. The crystals belonged to space group C2 and diffracted to 3.2 Å resolution. The transfer of glycosylphosphatidylinositol (GPI) anchors onto eukaryotic proteins is catalyzed by the transamidase complex, which is composed of at least five subunits (PIG-K, PIG-S, PIG-T, PIG-U and GPAA1). Here, the recombinant protein PIG-S_71–467 from Saccharomyces cerevisiae, including residues 71–467 of the entire 534-residue protein, was cloned, expressed and purified to homogeneity. The monodisperse protein was crystallized by the vapour-diffusion method. A diffraction data set was collected to 3.2 Å resolution with 91.6% completeness. The crystals belonged to space group C2, with unit-cell parameters a = 106.72, b = 59.33, c = 124.3 Å, β = 114.19°, and contained two molecules in the asymmetric unit