Glycosyltransferase catalyzing the last biosynthesis step of the N-glycan biosynthesis. Protein modification; protein glycosylation. Cell surface structure biogenesis; S-layer biogenesis. Reduced molecular weights of the S-layer glycoprotein and archaellins due to a change in the N-glycan composition. The tribranched hexasaccharide glycan of S-layer glycoprotein is a pentasaccharide that lacks a terminal hexose residue. Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.