Effects of glycosylation on protein structure, function and dynamics

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Recent years have seen remarkable progress in the field of structural biology of proteins. However, human or complex proteins with posttranslational modifications (like glycosylation, phosphorylation and methylation etc.) are rarely found in the Protein Data Bank (PDB), since these modifications cannot be performed sufficiently by prokaryotic protein expression hosts like Escherichia coli. Among the posttranslational modifications, protein glycosylation is the most abundant protein modification found in nature, introducing more diversity into the protein than all the other posttranslational modifications combined. Glycosylation of proteins changes their structure, thermodynamics and kinetics, which modulate the function of the proteins and influence their localization, trafficking, solubility, antigenicity, biological activity, half-life and cell-cell interactions. Therefore, it is not surprising that glycan structures and glycosylation patterns are highly dynamic and change during development and in certain diseases. So far, the effects of protein glycosylation on function are poorly understood. Even more, structural information regarding this posttranslational modification is rare. In fact, from a structural biology perspective glycosylation is undesired and is often considered as an additional obstacle to solve a protein structure due to the size, flexibility and heterogeneity of the oligosaccharide chains. In the Research Unit our group (P6 Schwalbe) wants to study the influence of glycosylation on the structure, function and dynamics of glycoproteins by NMR spectroscopy. For this purpose, we will develop specific NMR tools (expression, isotope labeling, NMR methods) to conduct research on glycosylated proteins in the first funding period. In the Research Unit we will focus on three highly conserved glycosylation pathways (N-glycosylation, C-mannosylation and O-mannosylation) which are based on the lipid dolichol and compete for both mannosyl donor substrates and acceptor proteins. In the course of the assembly of this Research Unit we already started to structurally investigate the effect of tryptophan C-mannosylation by NMR in collaboration with (P1 Bakker).