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GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
The Eukaryotic Cell SurfaceThe Eukaryotic Cell Surface
Lodish, et al. (1995) Molecular Cell Biology 3rd ed.Lodish, et al. (1995) Molecular Cell Biology 3rd ed.
lipid bilayerlipid bilayer
fibroblastfibroblast
extracellularextracellular
intracellularintracellular
Martinez-Palomo, A., et al. Cancer Res. 29, 925-937, 1969
HIV gp120HIV gp120HIV gp120HIV gp120
“Structure” of HIV gp120Zolla-Pazner (2004)Nature Reviews Immunol 4, 199
Burton DR et al (2012) Cell Host & Microbe 4:396
HIV gp120HIV gp120HIV gp120HIV gp120
Doores K J et al. (2010) PNAS 107:17107
Proteins fold onto Proteins fold onto themselves… themselves…
glycans spread out glycans spread out in spacein space
Thy-1cell-cell interaction
protein
1.5 kDa GPI
anchor
3 kDa N-linked
glycans
18 kDa protein
membrane
Second Edition
Essentials of Glycobiology
Roles of protein glycosylationRoles of protein glycosylation
• Protein folding*Protein folding*• Protein conformationProtein conformation• Protein trafficking*Protein trafficking*• Cell surface glycoprotein lattice*Cell surface glycoprotein lattice*• Regulation of signaling pathways*Regulation of signaling pathways*• Cell-cell interactions*Cell-cell interactions*
• Protein folding*Protein folding*• Protein conformationProtein conformation• Protein trafficking*Protein trafficking*• Cell surface glycoprotein lattice*Cell surface glycoprotein lattice*• Regulation of signaling pathways*Regulation of signaling pathways*• Cell-cell interactions*Cell-cell interactions*
* via glycan recognition* via glycan recognition
Protein Folding: Protein Folding:
N-linked protein glycosylation is essential for chaperone-assisted N-linked protein glycosylation is essential for chaperone-assisted folding of glycoproteins in the endoplasmic reticulum folding of glycoproteins in the endoplasmic reticulum
Helenius, A. and Aebi, M. (2001) Science 291, 2364-2369
Asn
http://www.cdgs.com/
Joel
Zachary
Megan
Protein Folding: Protein Folding:
Children with altered protein N-glycosylation have diverse motor, Children with altered protein N-glycosylation have diverse motor, physiological and cognitive deficits physiological and cognitive deficits
Protein Conformation: Protein Conformation: Closely spaced short O-linked glycans on mucinsClosely spaced short O-linked glycans on mucins
Protein Conformation: Protein Conformation: Conserved glycosylation of IgG is Conserved glycosylation of IgG is requiredrequired for interaction with for interaction with
immune effectors (complement, Fc-receptors) immune effectors (complement, Fc-receptors)
Protein Trafficking: Protein Trafficking: Unique glycosylation of lysosomal enzymes “labels” them for Unique glycosylation of lysosomal enzymes “labels” them for
trafficking to the lysosome via the Man-P receptor(s)trafficking to the lysosome via the Man-P receptor(s)
https://wikispaces.psu.edu/v
Asn
Cell surface glycoprotein lattice: Cell surface glycoprotein lattice: Sugar binding proteins (galectins) bind to Sugar binding proteins (galectins) bind to
and stabilize cell surface glycoproteinsand stabilize cell surface glycoproteins
Lau et al (2007) Cell 129:123
Altered glycoprotein glycans result in Altered glycoprotein glycans result in internalization of key glycoproteinsinternalization of key glycoproteins
Pancreatic β cells stained for Glut-2 (green), insulin (red), and DNA (blue). Ohtsubo et al (2005) Cell 123:1307
Regulation of signaling pathways: Regulation of signaling pathways: Notch signaling during development is driven by glycosylation
Stanley (2007) Curr Opin Struct Biol 17:530
Sharon and Lis (1993) Scientific American
Carbohydrate binding determinant
Carbohydrate recognition domain (CRD)
Glycans in cell-cell interactionsGlycans in cell-cell interactions
Lectin
Glycan
Roles of protein glycosylationRoles of protein glycosylation
• Protein folding*Protein folding*• Protein conformationProtein conformation• Protein trafficking*Protein trafficking*• Cell surface glycoprotein lattice*Cell surface glycoprotein lattice*• Regulation of signaling pathways*Regulation of signaling pathways*• Cell-cell interactions*Cell-cell interactions*
• Protein folding*Protein folding*• Protein conformationProtein conformation• Protein trafficking*Protein trafficking*• Cell surface glycoprotein lattice*Cell surface glycoprotein lattice*• Regulation of signaling pathways*Regulation of signaling pathways*• Cell-cell interactions*Cell-cell interactions*
* via glycan recognition* via glycan recognition
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
Modes of glycosylationModes of glycosylation
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
““N-linked” glycan linkage to protein asparagine residuesN-linked” glycan linkage to protein asparagine residues
N-glycosidicbond
N-linked glycanN-linked glycan
Major classes of N-linked glycansMajor classes of N-linked glycans
High mannose
Examples of structures found as termini on the branches Examples of structures found as termini on the branches of complex N-linked glycoprotein glycans….of complex N-linked glycoprotein glycans….
Terminal Saccharide Diversity --- A key to recognitionTerminal Saccharide Diversity --- A key to recognition
NeuAc NeuAc 2-6 Gal 2-6 Gal 1-4 GlcNAc---1-4 GlcNAc---NeuAc NeuAc 2-3 Gal 2-3 Gal 1-4 GlcNAc---1-4 GlcNAc---Gal Gal 1-3 Gal 1-3 Gal 1-4 GlcNAc---1-4 GlcNAc---4-SO4-SO33-GalNAc -GalNAc 1-4 GlcNAc---1-4 GlcNAc---
(-Gal (-Gal 1-4 GlcNAc 1-4 GlcNAc 1-3-)1-3-)nn = poly-N-acetyllactosamine = poly-N-acetyllactosamine
(n may be >6)(n may be >6)
(-NeuAc (-NeuAc 2-8-) 2-8-) nn = polysialic acid = polysialic acid
(n may be >50)(n may be >50)
Fuc residues Fuc residues (e.g. Fuc (e.g. Fuc 1-21-2 Gal; Fuc Gal; Fuc 1-3 GlcNAc; Fuc 1-3 GlcNAc; Fuc 1-4 GlcNAc1-4 GlcNAc
Human spleen
Human kidney
Human spleen Human kidneyHuman spleen Human kidney
N-linked glycosylation consensus sequenceN-linked glycosylation consensus sequence
The N-linked amino acid consensus The N-linked amino acid consensus sequence is “Asn-[any AA]- [Ser or Thr]” sequence is “Asn-[any AA]- [Ser or Thr]” where the middle amino acid is not Prowhere the middle amino acid is not Pro
GlycoformsGlycoforms
Whereas a protein is defined by its unique amino acid Whereas a protein is defined by its unique amino acid sequence, sequence, the glycan structure at a single protein the glycan structure at a single protein glycosylation site variesglycosylation site varies. .
Although glycan structures vary at each glycosylation Although glycan structures vary at each glycosylation site, the profile is reproducible, protein-specific, site-site, the profile is reproducible, protein-specific, site-specific, and cell type-specific.specific, and cell type-specific.
Three glycoforms of CD59, a compliment regulatory proteinThree glycoforms of CD59, a compliment regulatory protein
Human erythropoietin glycosylationHuman erythropoietin glycosylation
““Humanization” of Humanization” of yeast to produce yeast to produce complex N-linked complex N-linked glycoproteinsglycoproteins
Hamilton, et al. Hamilton, et al. Science Science 313, 1441-1443 (8 September 2006)313, 1441-1443 (8 September 2006)
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
“O-linked” glycan linkage to protein serine residues
O-linked glycanO-linked glycan
O-linked glycan O-linked glycan classes & diversityclasses & diversity
Human spleen
O-GlcNAc
Note: No further sugar substitutions have been confirmed
O-GlcNAc is localized to the cytoplasm and nucleus.O-GlcNAc is localized to the cytoplasm and nucleus.
O-GlcNAc is present in all higher eukaryotes studied.O-GlcNAc is present in all higher eukaryotes studied.
O-GlcNAc is as abundant as phosphorylation.O-GlcNAc is as abundant as phosphorylation.
UDP-GlcNAc is as abundant as ATP in some cell types. UDP-GlcNAc is as abundant as ATP in some cell types.
O-GlcNAc containing proteins are phosphoproteins.O-GlcNAc containing proteins are phosphoproteins.
O-GlcNAc and phosphorylation are often reciprocal.O-GlcNAc and phosphorylation are often reciprocal.
O-GlcNAc is dynamic, implying a regulatory role.O-GlcNAc is dynamic, implying a regulatory role.
Key Features of O-linked GlcNAc
Three-state model: unmodified / O-GlcNAc / phosphate
O-GlcNAc
GlycoproteinGlycoproteinUnmodified protein
Unmodified proteinPhosphoprotein
OPO32-
PhosphatasePhosphatase
OGTOGT
OGTOGT
PhosphatasePhosphatase
KinaseKinase
KinaseKinase
O-GlcNAcaseO-GlcNAcase
O-GlcNAcaseO-GlcNAcase
Natasha Zachara
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
Glycosyltransferase reactionGlycosyltransferase reaction(UDP-Gal:glucose (UDP-Gal:glucose ββ4 galactosyltransferase)4 galactosyltransferase)
nucleotide sugar donor acceptor glycoside
+
Sugar donorsSugar donors
http://www.cazypedia.org/index.php/Glycosyltransferase http://www.cazypedia.org/index.php/Glycosyltransferase
http://www.cazypedia.org/index.php/Glycosyltransferase http://www.cazypedia.org/index.php/Glycosyltransferase
Additional donor intermediatesAdditional donor intermediates
Diversity in glycosyltransferases – Diversity in glycosyltransferases – Example: 20 human sialyltransfearse genesExample: 20 human sialyltransfearse genes
“St3Gal ” genes (6)
“St6GalNAc ” genes (6)
“St6Gal ” genes (2)
“St8Sia ” genes (6)
General rule: at least one distinct enzyme for every linkage
Glycoprotein biosynthesisGlycoprotein biosynthesis
• N-Linked – en-bloc preconstructed core, trimming, N-Linked – en-bloc preconstructed core, trimming, terminal elaborationterminal elaboration
• O-Linked - sugar by sugar additionO-Linked - sugar by sugar addition• O-GlcNAc - dynamic transferase/glycosidaseO-GlcNAc - dynamic transferase/glycosidase
Glycolipid biosynthesisGlycolipid biosynthesis
• Stepwise sugar-by-sugar additionStepwise sugar-by-sugar addition• GPI Anchor – en-bloc preconstructed core, elaborationGPI Anchor – en-bloc preconstructed core, elaboration
Proteoglycan biosynthesisProteoglycan biosynthesis
• Stepwise sugar-by-sugar addition (core and repeating Stepwise sugar-by-sugar addition (core and repeating disaccharide)disaccharide)
• Post-polymerization modificationsPost-polymerization modifications
N-linked glycosylation starts with a lipid-linked intermediate: N-linked glycosylation starts with a lipid-linked intermediate: GlcGlc33ManMan99GlcNAcGlcNAc22-P-P-Dol-P-P-Dol
N-linked glycosylation: Core biosynthesis and transferN-linked glycosylation: Core biosynthesis and transfer
Freeze & Aebi (2005) Curr Opin Struct Biol 15:490Freeze & Aebi (2005) Curr Opin Struct Biol 15:490
N-linked glycosylation: Oligosaccharyltransferase (OST)N-linked glycosylation: Oligosaccharyltransferase (OST)
Mohorko et al (2011) J Inherit Metab Dis 34:869Mohorko et al (2011) J Inherit Metab Dis 34:869
N-linked glycosylation: Trimming and terminal elaborationN-linked glycosylation: Trimming and terminal elaboration
Freeze & Aebi (2005) Curr Opin Struct Biol 15:490Freeze & Aebi (2005) Curr Opin Struct Biol 15:490
Courtesy Hudson H. Freeze, Burnham Institute, La Jolla, CA
Congenital Disorders of Glycosylation (CDG)
Congenital Disorders of Glycosylation (CDG)
Freeze & Aebi (2005) Curr Opin Struct Biol 15:490Freeze & Aebi (2005) Curr Opin Struct Biol 15:490
Congenital Disorders of Glycosylation (CDG)
Freeze & Aebi (2005) Curr Opin Struct Biol 15:490Freeze & Aebi (2005) Curr Opin Struct Biol 15:490
GlycoproteinsGlycoproteinsGlycoproteinsGlycoproteins
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
• Roles of glycoprotein glycosylationRoles of glycoprotein glycosylation• Modes of glycoprotein glycosylationModes of glycoprotein glycosylation• N-linked glycansN-linked glycans• O-linked glycansO-linked glycans
– O-GalNAc – “mucin” type glycosylationO-GalNAc – “mucin” type glycosylation
– O-Man, O-Fuc, O-Glc, O-Xyl – signaling moleculesO-Man, O-Fuc, O-Glc, O-Xyl – signaling molecules
– O-GlcNAc – intracellular protein regulationO-GlcNAc – intracellular protein regulation
• Glycan BiosynthesisGlycan Biosynthesis– General PrinciplesGeneral Principles
– N-linked glycoprotein biosynthesisN-linked glycoprotein biosynthesis
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