Phosphatidylinositol Glycan W (PIGW)

Glycosylphosphatidylinositol (GPI) is a complex glycolipid that anchors many proteins to the cell surface. PIGW acts in the third step of GPI biosynthesis and acylates the inositol ring of phosphatidylinositol.By database searching for sequences similar to rat Pigw, Murakami et al. (2003) identified human PIGW. The deduced 504-amino acid protein contains 13 transmembrane domains and shares 77% sequence identity with the rat protein. Fractionation of a human lymphoblastoid cell line revealed that PIGW associated with the endoplasmic reticulum (ER). Murakami et al. (2003) determined that the N terminus and several conserved regions of rat Pigw face the lumen of the ER, whereas its C terminus is cytoplasmic.