Figure 4. O-Mannosyl Glycan of α-Dystroglycan.
The laminin-binding glycan of α-dystroglycan contains a core trisaccharide produced by POMT1/2, POMGnT2, and β3GalNT-2. The 6-OH position of mannose is phosphorylated by POMK, on which an unknown structure is added. β4GAT-1 makes an acceptor substrate for LARGE, which adds repeating GlcAβ(1–3)Xylα(1–3) units. The required roles of other associated enzymes such as FKTN are still unknown.