Involved in the assembly of a N-linked pentasaccharide that decorates the S-layer glycoprotein and flagellins. Catalyzes the addition of the mannose found at position 5 of the pentasaccharide to its own distinct dolichol phosphate carrier. Cell surface structure biogenesis; S-layer biogenesis. Mutants exhibit defective or limited motility. Belongs to the glycosyltransferase 2 family.