Glycoprotein

A Glycoprotein is a protein that contains oligosaccharide chains (glycans) covalently attached to amino acid side-chains.

• Example(s):
  • Hemagglutinin.
  • Erythropoietin.
  • in the form of a spike in a Viral Peplomer.
  • Glycoprotein enzyme, such as Prostate-Specific Antigen (PSA).
  • An Osteopontin.
  • …
• See: ABO Blood Group System, Oligosaccharide, Glycans, Amino Acid, Glycosylation, Secretory Protein, Integral Membrane Proteins, Cytosol.

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References

2020

• (Wikipedia, 2020) ⇒ https://en.wikipedia.org/wiki/glycoprotein Retrieved:2020-3-29.
  • Glycoproteins are proteins which contain oligosaccharide chains (glycans) covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. Secreted extracellular proteins are often glycosylated.

    In proteins that have segments extending extracellularly, the extracellular segments are also often glycosylated. Glycoproteins are also often important integral membrane proteins, where they play a role in cell–cell interactions. It is importantto distinguish endoplasmic reticulum-based glycosylation of the secretory system from reversible cytosolic-nuclear glycosylation. Glycoproteins of the cytosol and nucleus can be modified through the reversible addition of a single GlcNAc residue that is considered reciprocal to phosphorylation and the functions of these are likely to be additional regulatory mechanism that controls phosphorylation-based signalling. In contrast, classical secretory glycosylation can be structurally essential. For example, inhibition of asparagine-linked, i.e. N-linked, glycosylation can prevent proper glycoprotein folding and full inhibition can be toxic to an individual cell. In contrast, perturbation of glycan processing (enzymatic removal/addition of carbohydrate residues to the glycan), which occurs in both the endoplasmic reticulum and Golgi apparatus, is dispensable for isolated cells (as evidence by survival with glycosides inhibitors) but can lead to human disease (congenital disorders of glycosylation) and can be lethal in animal models. It is therefore likely that the fine processing of glycans is important for endogenous functionality, such as cell trafficking, but that this is likely to have been secondary to its role in host-pathogen interactions. A famous example of this latter effect is the ABO blood group system.

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