Regulates the biosynthesis of dolichol phosphate-mannose. Regulatory subunit of the dolichol-phosphate mannose (DPM) synthase complex; essential for the ER localization and stable expression of dpm1 (By similarity). Protein modification; protein glycosylation. Component of the dolichol-phosphate mannose (DPM) synthase complex composed of dpm1, dpm2 and dpm3. Belongs to the DPM2 family. The gene for this protein is duplicated in strains AX3 and AX4. These strains contain a duplication of a segment of 750 kb of chromosome 2 compared to the corresponding sequence in strain AX2.