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Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide 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 glycosylated. Glycoproteins are often important integral membrane proteins, where they play a role in cell–cell interactions. Glycoproteins are also formed in the cytosol, but their functions and the pathways producing these modifications in this compartment are less understood. ==Types of glycosylation== There are several types of glycosylation, although the first two are the most common. * In N-glycosylation, sugars are attached to nitrogen, typically on the amide side-chain of asparagine. * In O-glycosylation, sugars are attached to oxygen, typically on serine or threonine but also on non-canonical amino acids such as hydroxylysine & hydroxyproline. * In P-glycosylation, sugars are attached to phosphorus on a phosphoserine. * In C-glycosylation, sugars are attached directly to carbon, such as in the addition of mannose to tryptophan. * In glypiation, a GPI glycolipid is attached to the C-terminus of a polypeptide, serving as a membrane anchor. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「glycoprotein」の詳細全文を読む スポンサード リンク
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