protein glycosylation

Definition

Target type: biologicalprocess

A protein modification process that results in the addition of a carbohydrate or carbohydrate derivative unit to a protein amino acid, e.g. the addition of glycan chains to proteins. [GOC:curators, GOC:pr]

Protein glycosylation is a complex biological process that involves the attachment of carbohydrate units, known as glycans, to proteins. This process plays a crucial role in various cellular functions, including protein folding, stability, trafficking, and signaling. Glycosylation occurs in the endoplasmic reticulum (ER) and Golgi apparatus, where specialized enzymes called glycosyltransferases catalyze the addition of sugars to specific amino acid residues on proteins.

There are two main types of protein glycosylation: N-linked glycosylation and O-linked glycosylation. N-linked glycosylation involves the attachment of glycans to the nitrogen atom of asparagine residues, while O-linked glycosylation involves the attachment of glycans to the oxygen atom of serine or threonine residues.

N-linked glycosylation typically starts in the ER with the assembly of a precursor oligosaccharide, called GlcNAc2Man9Glc3, on a lipid carrier called dolichol phosphate. This precursor oligosaccharide is then transferred to the asparagine residue of a protein. Following transfer, the precursor oligosaccharide undergoes a series of modifications, including the removal of glucose and mannose residues, before being further processed in the Golgi apparatus. In the Golgi, the oligosaccharide undergoes a variety of trimming and addition reactions, resulting in a diverse range of complex glycans.

O-linked glycosylation is more diverse than N-linked glycosylation, with different types of glycans being added to proteins. O-linked glycosylation typically starts in the Golgi apparatus with the addition of a single N-acetylglucosamine (GlcNAc) residue to a serine or threonine residue. This initial GlcNAc can then be further modified by the addition of other sugars, resulting in a variety of O-linked glycans.

The glycan structures on proteins can vary significantly depending on the protein, the cell type, and the organism. This diversity in glycan structures contributes to the diverse functions of glycosylation. For instance, glycosylation can influence protein folding and stability by providing structural support and mediating interactions with other molecules. It also plays a role in protein trafficking, directing proteins to their correct cellular locations. Furthermore, glycosylation can modulate protein activity and signaling by affecting interactions with other proteins or receptors.

In addition to its diverse roles in cellular processes, protein glycosylation is also involved in various disease states. Alterations in glycosylation patterns have been associated with cancer, autoimmune diseases, and infectious diseases. For example, changes in the glycosylation of tumor cells can contribute to their increased growth and spread. Moreover, glycosylation plays a crucial role in the recognition of pathogens by the immune system, and alterations in glycosylation patterns can impair immune responses.

Overall, protein glycosylation is a complex and essential biological process that plays a critical role in various cellular functions and disease states. Understanding the mechanisms of glycosylation is crucial for developing new therapies for a wide range of diseases.'
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Proteins (11)

Compounds (47)