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Glycoproteins are
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s which contain
oligosaccharide An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sug ...
chains (
glycans The terms glycan and polysaccharide are defined by IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is ...
)
covalently A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they s ...
attached to
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
side-chains. The
carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
is attached to the protein in a cotranslational or
posttranslational modification Post-translational modification (PTM) refers to the covalent and generally enzyme, enzymatic modification of proteins following protein biosynthesis. Proteins are synthesized by ribosomes translation (biology), translating mRNA into polypeptide c ...
. This process is known as
glycosylation Glycosylation (see also chemical glycosylationA chemical glycosylation reaction involves the coupling of a glycosyl donor, to a glycosyl acceptor forming a glycoside. If both the donor and acceptor are sugars, then the product is an oligosacchar ...

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 An integral membrane protein (IMP) is a type of membrane protein Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Int ...
, where they play a role in cell–cell interactions. It is important to distinguish endoplasmic reticulum-based glycosylation of the secretory system from reversible cytosolic-nuclear glycosylation. Glycoproteins of the
cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a s ...
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 The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
and
Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that stu ...

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 The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigen In immunology Immunology is a branch of biology that covers the study of immune systems in all organisms. Immunology charts, measu ...
. Though there are different types of glycoproteins, the most common are N-linked and O-linked glycoproteins. These two types of glycoproteins each have structural differences that give them their names. Glycoproteins vary greatly in composition, making many different compounds such as antibodies or hormones. Due to the array of functions within the body, interest in glycoprotein synthesis for medical use has increased. There are now several methods to synthesize glycoproteins, including recombination and glycosylation of proteins. Glycosylation is also known to occur on nucleocytoplasmic proteins in the form of .


Types of glycosylation

There are several types of glycosylation, although the first two are the most common. * In
N-glycosylation ''N''-linked glycosylation, is the attachment of an oligosaccharide An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek wikt:ὀλίγος#Ancient Greek, ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a ...
, sugars are attached to nitrogen, typically on the
amide In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

amide
side-chain of
asparagine Asparagine (symbol Asn or N), is an α-amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compound ...

asparagine
. * In
O-glycosylation ''O''-linked glycosylation is the attachment of a sugar Sugar is the generic name for , soluble s, many of which are used in food. Simple sugars, also called s, include , , and . Compound sugars, also called s or double sugars, are molecul ...
, sugars are attached to oxygen, typically on
serine Serine (symbol Ser or S) is an α-amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, ...

serine
or
threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an Amine, α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated ...

threonine
, but also on
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemi ...

tyrosine
or non-canonical amino acids such as
hydroxylysine Hydroxylysine (Hyl) is an amino acid Amino acids are organic compounds that contain amino (–NH2) and Carboxylic acid, carboxyl (–COOH) functional groups, along with a Substituent, side chain (R group) specific to each amino acid. The key C ...

hydroxylysine
&
hydroxyproline (2''S'',4''R'')-4-Hydroxyproline, or L-hydroxyproline ( C5H9 O3 N), is an amino acid Amino acids are organic compounds that contain amino (–NH2) and Carboxylic acid, carboxyl (–COOH) functional groups, along with a Substituent, side chain ...

hydroxyproline
. * In P-glycosylation, sugars are attached to
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
on a
phosphoserine Phosphoserine (abbreviated as SEP or J) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a and an . s are s of ; they ...

phosphoserine
. * In C-glycosylation, sugars are attached directly to carbon, such as in the addition of
mannose Mannose is a sugar Sugar is the generic name for , soluble s, many of which are used in food. Simple sugars, also called s, include , , and . Compound sugars, also called s or double sugars, are molecules made of two monosaccharides joine ...

mannose
to
tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a non-polar Aromatic hydrocarbon, aromatic amino ...

tryptophan
. * In S-glycosylation, a beta- GlcNAc is attached to the sulfur atom of a
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the chemical formula, formula HOOC-CH-(NH2)-CH2-SH. The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. The thiol is suscepti ...

cysteine
residue. * In
glypiationGlypiation is the addition by covalent bonding of a glycosylphosphatidylinositol (GPI) anchor and is a common post-translational modification Post-translational modification (PTM) refers to the covalent and generally enzymatic modification of pr ...
, a GPI glycolipid is attached to the
C-terminus The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid Amino acids are organic compound In , organic compounds are generally any s that contain ...

C-terminus
of a
polypeptide Peptides (from Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the dialects of the Greek language spoken ...
, serving as a membrane anchor. * In
glycation Glycation (sometimes incorrectly called non-enzymatic glycosylation) is the covalent A covalent bond is a chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In cl ...
, also known as non-enzymatic glycosylation, sugars are covalently bonded to a protein or lipid molecule, without the controlling action of an enzyme, but through a
Maillard reaction The Maillard reaction ( ; ) is a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter In classical physics and general ...
.


Monosaccharides

Monosaccharides commonly found in eukaryotic glycoproteins include: The sugar group(s) can assist in
protein folding Protein folding is the physical process Physical changes are changes affecting the form of a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass ...

protein folding
, improve proteins' stability and are involved in cell signalling.


Structure

The critical structural element of all glycoproteins is having
oligosaccharides An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the su ...
bonded
covalently A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they s ...
to a protein. There are 10 common monosaccharides in mammalian
glycans The terms glycan and polysaccharide are defined by IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is ...

glycans
including:
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
(Glc),
fucose Fucose is a hexose In , a hexose is a (simple sugar) with six atoms. The chemical formula for all hexoses is C6H12O6, and their is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily convert into each other in aqueous ...

fucose
(Fuc), xylose (Xyl), mannose (Man), galactose (Gal), N-acetylglucosamine (GlcNAc), glucuronic acid (GlcA), iduronic acid (IdoA), N-acetylgalactosamine (GalNAc), sialic acid, and 5-N-acetylneuraminic acid (Neu5Ac). These glycans link themselves to specific areas of the protein
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
chain. The two most common linkages in glycoproteins are N-linked and O-linked glycoproteins. An N-linked glycoprotein has glycan bonds to the nitrogen containing an
Asparagine Asparagine (symbol Asn or N), is an α-amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compound ...

Asparagine
amino acid within the protein sequence. An O-linked glycoprotein is where the sugar is bonded to an oxygen atom of a
Serine Serine (symbol Ser or S) is an α-amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, ...

Serine
or
Threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an Amine, α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated ...

Threonine
amino acid in the protein. Glycoprotein size and composition can vary largely, with carbohydrate composition ranges from 1% to 70% of the total mass of the glycoprotein. Within the cell, they appear in the blood, the
extracellular matrix In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...
, or on the outer surface of the plasma membrane, and make up a large portion of the proteins secreted by eukaryotic cells. They are very broad in their applications and can function as a variety of chemicals from antibodies to hormones.


Glycomics

Glycomis is the study of the carbohydrate components of cells. Though not exclusive to glycoproteins, it can reveal more information about different glycoproteins and their structure. 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. Historically, mass spectrometry has been used to identify the structure of glycoproteins and characterize the carbohydrate chains attached.


Examples

The unique interaction between the oligosaccharide chains have different applications. First, it aids in quality control by identifying misfolded proteins. The oligosaccharide chains also change the solubility and polarity of the proteins that they are bonded to. For example, if the oligosaccharide chains are negatively charged, with enough density around the protein, they can repulse proteolytic enzymes away from the bonded protein. The diversity in interactions lends itself to different types of glycoproteins with different structures and functions. One example of glycoproteins found in the body is
mucin Mucins () are a family of high molecular weight A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically Electricity is the set of physical ph ...

mucin
s, which are secreted in the mucus of the respiratory and digestive tracts. The sugars when attached to mucins give them considerable water-holding capacity and also make them resistant to
proteolysis Proteolysis is the breakdown of protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. ...

proteolysis
by digestive enzymes. Glycoproteins are important for
white blood cell White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from Ancient Greek, Greek: ...
recognition. Examples of glycoproteins in the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such ...
are: * molecules such as
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and Viral disease, viruses. The antibody recognizes a unique mo ...

antibodies
(immunoglobulins), which interact directly with
antigen In immunology Immunology is a branch of biology that covers the study of immune systems in all organisms. Immunology charts, measures, and contextualizes the Physiology, physiological functioning of the immune system in states of both health ...
s. * molecules of the ''
major histocompatibility complex The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are ca ...
'' (or MHC), which are expressed on the surface of cells and interact with
T cell A T cell is a type of lymphocyte A lymphocyte is a type of white blood cell in the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from Ancient Greek, Greek: ...
s as part of the adaptive immune response. *sialyl Lewis X antigen on the surface of leukocytes. H antigen of the ABO blood compatibility antigens. Other examples of glycoproteins include: * gonadotropins (luteinizing hormone a follicle-stimulating hormone) *
glycoprotein IIb/IIIa In medicine, glycoprotein IIb/IIIa (GPIIb/IIIa, also known as integrin αIIbβ3) is an integrin complex found on platelets. It is a receptor for fibrinogen and von Willebrand factor and aids coagulation#Platelet activation, platelet activation. The ...
, an integrin found on
platelet Platelets, also called thrombocytes (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. ...

platelet
s that is required for normal platelet aggregation and adherence to the
endothelium Endothelium is a single layer of squamous Epithelium () is one of the four basic types of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. Wit ...
. * components of the
zona pellucida The zona pellucida (plural zonae pellucidae, also egg coat or pellucid zone) is a glycoprotein Glycoproteins are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions ...

zona pellucida
, which surrounds the
oocyte An oocyte (, ), oöcyte, ovocyte, or rarely ocyte, is a female gametocyte A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called ''sperm ...
, and is important for
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
-egg interaction. * structural glycoproteins, which occur in
connective tissue Connective tissue is one of the many basic types of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions ...
. These help bind together the fibers, cells, and ground substance of
connective tissue Connective tissue is one of the many basic types of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions ...
. They may also help components of the tissue bind to inorganic substances, such as
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
in
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
. * Glycoprotein-41 (
gp41 Gp41 also known as glycoprotein 41 is a subunit of the envelope protein complex A protein complex or multiprotein complex is a group of two or more associated polypeptide chain Peptides (from Greek language Greek (modern , romanized: ''E ...
) and glycoprotein-120 (
gp120 Envelope glycoprotein GP120 (or gp120) is a glycoprotein exposed on the surface of the Structure and genome of HIV, HIV envelope. It was discovered by Professors Tun-Hou Lee and Max Essex, Myron "Max" Essex of the Harvard School of Public Health ...
) are HIV viral coat proteins. Soluble glycoproteins often show a high
viscosity The viscosity of a fluid In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, ...

viscosity
, for example, in
egg white Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An ...
and
blood plasma Blood plasma is a yellowish liquid component of blood Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the Cell (biology), cells and transports metabolic waste products ...
. *
Miraculin Miraculin is a :Taste modifiers, taste modifier, a glycoprotein extracted from the fruit of ''Synsepalum dulcificum''. The berry, also known as the miracle fruit, was documented by explorer Chevalier des Marchais, who searched for many different ...

Miraculin
, is a glycoprotein extracted from ''
Synsepalum dulcificum ''Synsepalum dulcificum'' is a plant in the ''Sapotaceae'' family known for its Berry (botany), berry that, when eaten, causes sour foods (such as lemons and lime (fruit), limes) subsequently consumed to taste sweetness, sweet. This effect is du ...
'' a
berry A berry is a small, pulpy, and often edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who speci ...

berry
which alters human tongue receptors to recognize sour foods as sweet.
Variable surface glycoprotein Variant surface glycoprotein (VSG) is a ~60kDa protein which densely packs the Cell membrane, cell surface of protozoan Parasitism, parasites belonging to the genus ''Trypanosoma''. This genus is notable for their cell surface proteins. They were f ...
s allow the sleeping sickness ''Trypanosoma'' parasite to escape the immune response of the host. The viral spike of the human immunodeficiency virus is heavily glycosylated. Approximately half the mass of the spike is glycosylation and the glycans act to limit antibody recognition as the glycans are assembled by the host cell and so are largely 'self'. Over time, some patients can evolve antibodies to recognise the HIV glycans and almost all so-called 'broadly neutralising antibodies (bnAbs) recognise some glycans. This is possible mainly because the unusually high density of glycans hinders normal glycan maturation and they are therefore trapped in the premature, high-mannose, state. This provides a window for immune recognition. In addition, as these glycans are much less variable than the underlying protein, they have emerged as promising targets for vaccine design. P-glycoproteins are critical for antitumor research due to its ability block the effects of antitumor drugs. P-glycoprotein, or multidrug transporter (MDR1), is a type of ABC transporter that transports compounds out of cells. This transportation of compounds out of cells includes drugs made to be delivered to the cell, causing a decrease in drug effectiveness. Therefore, being able to inhibit this behavior would decrease P-glycoprotein interference in drug delivery, making this an important topic in drug discovery. For example, P-Glycoprotein causes a decrease in anti-cancer drug accumulation within tumor cells, limiting the effectiveness of chemotherapies used to treat cancer.


Hormones

Hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

Hormone
s that are glycoproteins include: *
Follicle-stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also call ...
*
Luteinizing hormone Luteinizing hormone (LH, also known as lutropin and sometimes lutrophin) is a hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic R ...
*
Thyroid-stimulating hormone Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the ne ...
*
Human chorionic gonadotropin Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantatio ...
*
Alpha-fetoprotein Alpha-fetoprotein (AFP, α-fetoprotein; also sometimes called alpha-1-fetoprotein, alpha-fetoglobulin, or alpha fetal protein) is a protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid ...
*


Distinction between glycoproteins and

proteoglycans Proteoglycans are protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958 ...

Quoting from recommendations for IUPAC:


Functions


Analysis

A variety of methods used in detection, purification, and structural analysis of glycoproteins are


Synthesis

The glycosylation of proteins has an array of different applications from influencing cell to cell communication to changing the thermal stability and the folding of proteins. Due to the unique abilities of glycoproteins, they can be used in many therapies. By understanding glycoproteins and their synthesis, they can be made to treat cancer,
Crohn's Disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea (which may be bloody if inflammation is severe), fever, abdominal distension, ...

Crohn's Disease
, high cholesterol, and more. The process of glycosylation (binding a carbohydrate to a protein) is a
post-translational modification Post-translational modification (PTM) refers to the covalent and generally enzyme, enzymatic modification of proteins following protein biosynthesis. Proteins are synthesized by ribosomes translation (biology), translating mRNA into polypeptide c ...
, meaning it happens after the production of the protein. Glycosylation is a process that roughly half of all human proteins undergo and heavily influences the properties and functions of the protein. Within the cell, glycosylation occurs in the
endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
.


Recombination

There are several techniques for the assembly of glycoproteins. One technique utilizes . The first consideration for this method is the choice of host, as there are many different factors that can influence the success of glycoprotein recombination such as cost, the host environment, the efficacy of the process, and other considerations. Some examples of host cells include E. coli, yeast, plant cells, insect cells, and mammalian cells. Of these options, mammalian cells are the most common because their use does not face the same challenges that other host cells do such as different glycan structures, shorter half life, and potential unwanted immune responses in humans. Of mammalian cells, the most common cell line used for recombinant glycoprotein production is the
Chinese hamster ovary Chinese hamster ovary (CHO) cells are an epithelial Epithelium is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of ...
line. However, as technologies develop, the most promising cell lines for recombinant glycoprotein production are human cell lines.


Glycosylation

The formation of the link between the glycan and the protein is key element of the synthesis of glycoproteins. The most common method of glycosylation of N-linked glycoproteins is through the reaction between a protected glycan and a protected Asparagine. Similarly, an O-linked glycoprotein can be formed through the addition of a
glycosyl A glycosyl group is a univalent free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular ...
donor with a protected
Serine Serine (symbol Ser or S) is an α-amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, ...

Serine
or
Threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an Amine, α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated ...

Threonine
. These two methods are examples of natural linkage. However, there are also methods of unnatural linkages. Some methods include ligation and a reaction between a serine-derived sulfamidate and thiohexoses in water. Once this linkage is complete, the amino acid sequence can be expanded upon using solid-phase peptide synthesis.


See also

* Ero1 *
Female sperm storage Female sperm storage is a biological process and often a type of sexual selection in which spermatozoa, sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, ...
*
Glycocalyx The glycocalyx, also known as the pericellular matrix, is a glycoprotein Glycoproteins are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, inclu ...

Glycocalyx
* Glycome *
Glycopeptide Glycopeptides are peptides that contain carbohydrate Moiety (chemistry), moieties (glycans) Covalent bond, covalently attached to the side chains of the amino acid residues that constitute the peptide. Over the past few decades it has been recog ...
*
Gp120 Envelope glycoprotein GP120 (or gp120) is a glycoprotein exposed on the surface of the Structure and genome of HIV, HIV envelope. It was discovered by Professors Tun-Hou Lee and Max Essex, Myron "Max" Essex of the Harvard School of Public Health ...
*
Gp41 Gp41 also known as glycoprotein 41 is a subunit of the envelope protein complex A protein complex or multiprotein complex is a group of two or more associated polypeptide chain Peptides (from Greek language Greek (modern , romanized: ''E ...
*
Miraculin Miraculin is a :Taste modifiers, taste modifier, a glycoprotein extracted from the fruit of ''Synsepalum dulcificum''. The berry, also known as the miracle fruit, was documented by explorer Chevalier des Marchais, who searched for many different ...

Miraculin
*
P-glycoprotein P-glycoprotein 1 (permeability glycoprotein, abbreviated as P-gp or Pgp) also known as multidrug resistance protein 1 (MDR1) or ATP-binding cassette sub-family B member 1 (ABCB1) or cluster of differentiation 243 (CD243) is an important protein o ...
*
Proteoglycan Proteoglycans are protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958 ...
*
Ribophorin''Ribophorins'' are dome shaped transmembrane glycoproteins which are located in the membrane of the rough endoplasmic reticulum, but are absent in the membrane of the smooth endoplasmic reticulum. There are two types of ribophorines: ribophorin I an ...
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Glycan The terms glycan and polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () using as catal ...

Glycan
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Protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

Protein
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Monosaccharides Monosaccharides (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...


Notes and references


Further reading

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External links

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