Phosphatidylinositol Glycan X (PIGX)

PIGX encodes a type I transmembrane protein in the endoplasmic reticulum (ER). The protein is an essential component of glycosylphosphatidylinositol-mannosyltransferase I, which transfers the first of the four mannoses in the GPI-anchor precursors during GPI-anchor biosynthesis. Studies in rat indicate that the protein is translated from a non-AUG translation initiation site. Alternative splicing results in multiple transcript variants.

The deduced 252-amino acid protein has a 22-amino acid signal peptide, a C-terminal transmembrane region, and 2 N-glycosylation sites. Human and rat Pigx proteins share 77% sequence identity. Pigx colocalized with an ER marker in transfected CHO cells.