Involved in the assembly of a N-linked pentasaccharide that decorates the S-layer glycoprotein and flagellins. Transfers mannose, the terminal pentasaccharide residue, from its dedicated dolichol phosphate carrier to the protein-bound glycan comprising the first four subunits of the N-linked pentasaccharide. Cell surface structure biogenesis; S-layer biogenesis. Protein modification; protein glycosylation. Mutants lack the final mannose subunit of the N-linked pentasaccharide.