Essential component of the GPI mannosyltransferase 2 complex. Responsible for the transfer of the second mannose to the glycosylphosphatidylinositol during GPI precursor assembly. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Part of the GPI mannosyltransferase 2 complex composed of GPI18 and PGA1. Present with 6940 molecules/cell in log phase SD medium.