Carbohydrates of influenza virus. Structural elucidation of the individual glycans of the FPV hemagglutinin by two-dimensional 1H n.m.r. and methylation analysis.

Abstract

The structures of the oligosaccharides of the hemagglutinin of fowl plague virus [influenza A/FPV/Rostock/34 (H7N1)] have been elucidated by one‐ and two‐dimensional 1H n.m.r. spectroscopy at 500 MHz and by microscale methylation analysis. N‐Glycosidic oligosaccharides of the oligomannosidic (OM) and of the N‐acetyllactosaminic type have been found, the latter type comprising biantennary structures, without (A) or with (E) bisecting N‐acetylglucosamine, and triantennary (C) structures. Analysis of the tryptic and thermolytic glycopeptides of the hemagglutinin allowed the allocation of these oligosaccharides to the individual glycosylation sites. Each attachment site contained a unique set of oligosaccharides. Asn12 contains predominantly structures C and E which are highly fucosylated. Asn28 contains OM and A structures that lack fucose and sulfate. Asn123 shows A that has incomplete antennae but is highly fucosylated and sulfated. Asn149 has fucosylated A and E. Asn231 shows fucosylated A and E with incomplete antennae. Asn406 has OM oligosaccharides. Asn478 has A and E with little fucose. Localization of the oligosaccharides on the three‐dimensional structure of the hemagglutinin revealed that the oligomannosidic glycans are attached to glycosylation sites at which the enzymes responsible for carbohydrate processing do not have proper access. These observations demonstrate that an important structural determinant for the oligosaccharide side chains is the structure of the glycoprotein itself. In addition, evidence was obtained that the rate of glycoprotein synthesis also has an influence on carbohydrate structure.

A human serum mannose-binding protein inhibits in vitro infection by the human immunodeficiency virus.

“…It has been suggested by Laskey et al (27) that this CD4 interaction site of gp120 may be found in a cleft, hence rendering it relatively antigenically inaccessible . This same tertiary conformation may explain the presence of high chains at these sites as steric accessibility of oligosaccharides is an important factor in processing of high mannose oligosaccharides to complex sugars (28,29). The conservation of this region and the potential glycosylation sites in different isolates of HIV I as well as between HIV I and HIV 2 (30), raises the possibility that these high mannose glycans could provide conserved targets for potential therapeutic agents .…”

Core region of Citrobacter lipopolysaccharide from strain PCM 1487

“…The failure to observe this crosspeak can be ascribed to the ineffective magnetization transfer in the case of protons sharing a small coupling constant and to the effects of a short transverse relaxation time, T2. Such difficulties were encountered for mannose residues of glycopeptides [24] (and references therein) and galactose residues of glycosphingolipids [25] and discussed at some length in a review article [26]. The distribution of signal intensity among several slightly different components of the heterogeneous sample is a further factor impeding the formation of detectable crosspeaks.…”

Glycans on influenza hemagglutinin affect receptor binding and immune response

“…Both regions carry N-linked oligosaccharides (9), which affect the functional properties of HA (10,11). Among different subtypes of influenza A viruses, there is extensive variation in the glycosylation sites of the head region, whereas the stem oligosaccharides are more conserved and required for fusion activity (11).…”