Human IgG Subclasses Differ in the Structural Elements of Their -Glycosylation.

Although immunoglobulin G (IgG) harbors just one -glycosylation site per heavy chain, this glycosylation plays a key role in modulating its function. In human serum, IgG is classified into four subclasses (IgG1, IgG2, IgG3, IgG4), each characterized by unique features in their sequences, disulfide bridges and glycosylation signatures. While protein glycosylation is typically studied at the compositional level, this severely underestimates the complexity of the molecules involved.

Complex -glycans are important for interspecies transmission of H7 influenza A viruses.

Influenza A viruses (IAVs) can overcome species barriers by adaptation of the receptor-binding site of the hemagglutinin (HA). To initiate infection, HAs bind to glycan receptors with terminal sialic acids, which are either -acetylneuraminic acid (NeuAc) or -glycolylneuraminic acid (NeuGc); the latter is mainly found in horses and pigs but not in birds and humans. We investigated the influence of previously identified equine NeuGc-adapting mutations (S128T, I130V, A135E, T189A, and K193R) in avian H7 IAVs and .

Glycoproteomics-Compatible MS/MS-Based Quantification of Glycopeptide Isomers.

Glycosylation is an essential protein modification occurring on the majority of extracellular human proteins, with mass spectrometry (MS) being an indispensable tool for its analysis, that not only determines glycan compositions, but also the position of the glycan at specific sites via glycoproteomics. However, glycans are complex branching structures with monosaccharides interconnected in a variety of biologically relevant linkages, isomeric properties that are invisible when the readout is mass alone. Here, we developed an LC-MS/MS-based workflow for determining glycopeptide isomer ratios.