Figure 1
From: Unravelling the Role of O-glycans in Influenza A Virus Infection
(A) N-acetylneuraminic acid (Neu5Ac, sialic acid (Sia)). (B) Standard receptor analogues Sialyl-Lac/LacNAc fragments: α(2,3)-sialyllactose [3′SL, Neu5Acα(2,3)Galβ(1,4)Glc], α(2,3)-sialyllactosamine (3′SLN, Neu5Acα(2,3)Galβ(1,4)GlcNAc]), α(2,6)-sialyllactose [6′SL, Neu5Acα(2,6)Galβ(1,4)Glc], α(2,6)-sialyllactosamine (6′SLN, Neu5Acα(2,6)Galβ(1,4)GlcNAc]). (C) Overview of the biosynthesis of sialylated core 1 O-glycans: The O-glycosylation is initiated by linking GalNAc to a serine or threonine via polypeptide-N-acetylgalactosaminyl-transferases (ppGalNAcTs). Core 1 β(1,3)galactosyltransferase (C1GalT1) adds a Gal residue to form the core 1 [T antigen, Galβ(1,3)GalNAcα-Ser/Thr]45. Core 1 can be substituted with Neu5Ac catalyzed by ST3 β-galactoside α(2,3)-sialyltransferase 1 and 2 (ST3Gal1 and 2) forming Neu5Acα(2,3)Galβ(1,3)GalNAcα-Ser/Thr (3-sialyl core 1)46. ST6 α-N-acetyl-neuraminyl-(2,3)-β-galactosyl-1,3-N-acetylgalactose-aminide-α(2,6)-sialyltransferase 1 and 2 (ST6GalNAc1 and 2) catalyze the formation of the disialylated core 1 [Neu5Acα(2,6)[Neu5Acα(2,3)Galβ(1,3)]GalNAcα-Ser/Thr; 3,6-disialyl core 1] and Neu5Acα(2,6)[Galβ(1,3)]GalNAcα-Ser/Thr (6-sialyl core 1)47,48.
