Figure 1.
(A) Examples of N-linked glycans present on gp120. (a) Oligomannose or high-mannose (Man9) type glycans, (b) hybrid type glycans, (c) tri- and (d) bi-antennary complex type glycans. N is asparagine; X is any amino acid except proline; S is serine and T is threonine. The abbreviations for the sugar units are: Fuc is fucose; Gal is galactose; GlcNAc is N-acetylglucosamine; Man is mannose and SA is sialic acid. The common pentasaccharide core unit is also marked in blue; (B) HIV-1 gp120 amino acid sequence and glycosylation sites. Alignment of the gp120 envelope protein sequences of the T cell line adapted HIV-1 strains IIIB and NL4.3. The N-glycosylation sites are shown in grey and the sequon numbers in red. The N397 glycan is not present in the viral strain we used due to the NSTWS sequence deletion as indicated in brackets. The N463 glycan is only present as N461 in our laboratory HIV-1 NL4.3 wild-type strain and not in the sequenced HIV-1 IIIB wild-type strain.