Stabilizer subunit of the dolichol-phosphate mannose (DPM) synthase complex; tethers catalytic subunit DPM1 to the endoplasmic reticulum. Protein modification; protein glycosylation. Component of the dolichol-phosphate mannose (DPM) synthase complex composed of DPM1, DPM2 and DPM3; within the complex, associates with DPM1 via its C-terminal domain and with DPM2 via its N-terminal portion (PubMed:10835346, PubMed:19576565). This interaction stabilizes DPM1 protein (PubMed:19576565). The disease may be caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the DPM3 family.