Editing Glycoprotein (section)

== Structure ==
[[File:Glycosylation of a polypeptide.png|thumb|487x487px|''N''-linked and ''O''-linked glycoproteins]]
The critical structural element of all glycoproteins is having [[oligosaccharide]]s bonded [[Covalent bond|covalently]] to a protein.<ref name="Lehninger_2013" /> There are 10 common monosaccharides in mammalian [[glycan]]s including: [[glucose]] (Glc), [[fucose]] (Fuc), [[xylose]] (Xyl), [[mannose]] (Man), [[galactose]] (Gal), N-[[acetylglucosamine]] (GlcNAc), [[glucuronic acid]] (GlcA), [[iduronic acid]] (IdoA), [[N-Acetylgalactosamine|N-acetylgalactosamine]] (GalNAc), [[sialic acid]], and 5-[[N-Acetylneuraminic acid|N-acetylneuraminic acid]] (Neu5Ac).<ref name="Picanco_e_Castro_2018" /> These glycans link themselves to specific areas of the protein [[amino acid]] chain.

The two most common linkages in glycoproteins are ''N''-linked and ''O''-linked glycoproteins.<ref name="Picanco_e_Castro_2018" /> An ''N''-linked glycoprotein has glycan bonds to the nitrogen containing an [[asparagine]] amino acid within the protein sequence.<ref name="Lehninger_2013" /> An ''O''-linked glycoprotein has the sugar is bonded to an oxygen atom of a [[serine]] or [[threonine]] amino acid in the protein.<ref name="Lehninger_2013" />

Glycoprotein size and composition can vary largely, with carbohydrate composition ranges from 1% to 70% of the total mass of the glycoprotein.<ref name="Lehninger_2013" /> Within the cell, they appear in the blood, the [[extracellular matrix]], or on the outer surface of the plasma membrane, and make up a large portion of the proteins secreted by eukaryotic cells.<ref name="Lehninger_2013" /> They are very broad in their applications and can function as a variety of chemicals from antibodies to hormones.<ref name="Lehninger_2013" />

=== Glycomics ===
[[Glycomics]] is the study of the carbohydrate components of cells.<ref name="Lehninger_2013" /> Though not exclusive to glycoproteins, it can reveal more information about different glycoproteins and their structure.<ref name="Lehninger_2013" /> One of the purposes of this field of study is to determine which proteins are glycosylated and where in the amino acid sequence the glycosylation occurs.<ref name="Lehninger_2013" /> Historically, mass spectrometry has been used to identify the structure of glycoproteins and characterize the carbohydrate chains attached.<ref name="Lehninger_2013" /><ref name = "Dell_2001">{{cite journal |vauthors=Dell A, Morris HR |title=Glycoprotein structure determination by mass spectrometry |journal=Science |volume=291 |issue=5512 |pages=2351–2356 |date=March 2001 |pmid=11269315 |doi=10.1126/science.1058890 |bibcode=2001Sci...291.2351D |s2cid=23936441}}</ref>