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 DPMS1. Protein modification; protein glycosylation. Component of the dolichol-phosphate mannose (DPM) synthase complex composed of DPMS1, DPMS2 and DPMS3; in the complex interacts directly with DPMS1 and DPMS2. May serve as regulatory subunit and membrane anchor for DPMS1. No visible phenotype under normal growth conditions. Belongs to the DPM3 family.