Glycoproteins as cell-surface structural components

The major cell-surface component of Halobacterium salinarium is a glycoprotein having structural and biosynthetic features in common with eukaryotic glycoproteins. The occurrence of glycoproteins in eukaryotes and archaebacteria suggests that they may have originated in primitive cells, which existed before the divergence of the three major lines of descent, possibly as structural components to stabilize the cell membrane.