Mannosyltransferase involved in glycosylphosphatidylinositol-anchor biosynthesis. Transfers the second mannose to the glycosylphosphatidylinositol during GPI precursor assembly. Required for the GPI-mediated endoplasmic reticulum exit and proper targeting to the cell surface of chp. Required for GPI-mediated membrane attachment of chp, qsm and Cont. Essential for microvillar stability in the rhabdomere. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Homozygous lethal. Belongs to the PIGV family. Was originally (PubMed:11102367) named veg. However, more thorough studies (PubMed:22575127) found that the veg phenotype does not map to this protein. It is still not known which gene corresponds to the veg phenotype. Truncated N-terminus.