S-layer protein. The S-layer is a paracrystalline mono-layered assembly of proteins which coat the surface of the cell. This archaeon is covered by an S-layer with hexagonal symmetry. S-layer glycoproteins are anchored to the plasma membrane as well as being surface-exposed (PubMed:2123862, PubMed:1569073). Bound to the membrane via a covalent lipid-mediated ArtA-dependent anchoring mechanism (PubMed:26712937). The glycoprotein is arranged on a p6 lattice with a lattice constant of 16.8 nm. It forms 4.5 nm high, dome-shaped, morphological complexes with a narrow pore at the apex opening into a 'funnel' towards the cell membrane (PubMed:16453843). O-glycosylated on 4 to 6 threonine residues; glycans consist of Glc-Gal disaccharides. The N-terminus is not blocked. Cleaved by the archaeosortase ArtA at the C-terminus, with removal of a short hydrophobic segment. Lipidation: Following protein translocation across the membrane, the protein is modified by a derivative of mevalonic acid (PubMed:12069685, PubMed:26712937). Lipid modification is ArtA-dependent and requires the conserved C-terminal PGF motif (PubMed:26712937). Asn-47 and Asn-117 are glycosylated by a pentasaccharide comprising a hexose, 2 hexuronic acids, a methyl ester of a hexuronic acid and mannose (PubMed:17996897, PubMed:20802039, PubMed:20149102). The pentasaccharide is produced in 2 steps: first, a tetrasaccharide is built on dolichol-P and then transferred to the S-layer glycoprotein. Then, the mannose fifth sugar is attached to a distinct molecule of dolichol-P and is transferred to the protein already carrying the tetrasaccharide (PubMed:21091511). The pentasaccharide on Asn-47 was initially thought to contain mannose, galactose, glucose and idose with a relative ratio of 1/3/3/0.2 (PubMed:1569073). However, it was later shown that it is not the case (PubMed:17996897). Under low-salt conditions (1.75 M instead of 3.4 M), a tetrasaccharide consisting of a sulfated hexose, 2 hexoses and rhamnose is attached to Asn-532 (PubMed:22029420). Belongs to the halobacterial S-layer protein family.