Phosphatidylinositol Glycan M (PIGM)

Glycosylphosphatidylinositol (GPI) is a membrane anchor for many cell surface proteins. It is a complex glycolipid that is attached to proteins containing a GPI attachment site. The biosynthesis of GPI involves the sequential addition of sugars to phosphatidylinositol. PIGM transfers the first mannose from dolichol-phosphate-mannose to phosphatidylinositol, initiating synthesis of the 3-mannose GPI core.

The deduced 423-amino acid protein has 10 transmembrane domains and a conserved DXD motif in a hydrophilic region following the first transmembrane domain. The DXD motif binds manganese and has a role in binding nucleotide sugar substrates. Transfection experiments in CHO cells localized PIGM to the endoplasmic reticulum.