Pga1 is found only in yeasts and not in mammals. It localises in the ER as a glycosylated integral membrane protein. It binds to the GPI-mannosyltransferase II subunit of the GPI and it is responsible for the second mannose addition to GPI precursors. The GPI-anchoring complex is a glycolipid that functions as a membrane anchor for many cell-surface proteins [1].

1: Pga1 is an Essential Component of Glycosylphosphatidylinositol-Mannosyltransferase II of Saccharomyces cerevisiae. Sato K, Noda Y, Yoda K; Mol Biol Cell. 2007; [Epub ahead of print] PMID:17615295