Fig. 2.

Sugar moieties on UPIa and Ib. UPIa and Ib possess four transmembrane domains (TD) (shown as cylinders) containing conserved aa residues. TD1 and TD2 are connected via a small extracellular loop (EC1), and TD3 and TD4 via a large extracellular loop (EC2). The main glycovariant of UPIa contain a high-mannose glycan linked to Asn-169 (a), whereas UPIb has a tetraantennary fucosylated complex glycan linked at Asn-131 (b). Abbreviations: Asn asparagine; Gal galactose; GlcNAc N-Acetylglucosamine; Fuc fucose; Man mannose