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11 Cards in this Set
- Front
- Back
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Basic Structural Elements of Proteoglycans
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2 forms exist (N linked (most abundant) and O linked)
branched structures w/o repeating units carb does not cross link peptide chain heterogenous Carb can be added non – enzymatically (ie. In Diabetes) Determine blood type; only diff b/c a and b is terminal sugar |
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N linked proteoglycan
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All have core pentasaccharide
2 types exist; complex and mannose Glycosylation site is sequence specific; uses Asn, and Serine and Threonine are candidates In Golgi and ER |
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O linked proteoglycan
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few common features
added in Golgi posttranslationally N and O linkages can exist together on one protein Only in Golgi |
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Synthesis of N linked Glycoproteins
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Dolichol Pyrophosphate – lipid soluable carrier upon which oligosaccharides are constructed
A. Protein synthesis begins and peptide chain moves to ER B. A branched oligosaccharide is created with a dolichol pyrophosphate attached C. The oligosaccharide is transferred from the Dolichol to an Aspargine (ASN) residue of the growing peptide chain D. Trimming of peptide chain occurs as it moves through ER E. In the golgi, further trimming, or adding of monosaccharides occurs |
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Glycoprotein synthesis general
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How you put a carb on or off is a very specific process
Each step occurs one at a time Donor sugar has to be in the activated form Each step has a different enzyme |
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Imp pts of N
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The precursor oligosaccharide constructed on dolichol pyrophosphate is co-translationally transferred as a block of 14 sugars to a specific asparagine residue in the growing polypeptide chain in the ER lumen.
Some sugars are then trimmed before sending the glycoprotein to the Golgi where further trimming and/or addition of monosaccahrides occurs. |
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O linked glycoprotein synthesis
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O-linked glycoproteins are NOT synthesized via the dolichol phosphate cycle. Their synthesis:
is post-translational occurs in the Golgi is catalyzed by individual glycosyl transferases |
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Structural Elements of GAGS and proteoglycans
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Proteoglycans; aka mucans
Found in CT PGs contain large polymers of glycosaminoglycans (GAGs) which are repeating disaccharides that are highly negative due to sulfate and carboxylate groups Fx: tensil strength, rigidity resilience, elasticity substratum for cell signaling/development, differentiation Huge Carbohydrate concentration Contain a lot of water, but can be compressed (joints, eyelids..) 6 classes of GAGS; 5 attach to proteins; exception Hyoluronic Acid Look like a bottle brush Example = heparin |
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Proteoglycans
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Glycosaminoglycans are long, linear polymers of repeating disaccharide units. When linked to a core protein, they form proteoglycans
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Lysosomal Storage Dz
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a. I-cell disease is due to a defective sorting of glycoproteins; can’t phosphorylate mannos
b. lysosomal storage diseases are due to defects in the glycosyl hydrolazes c. Defects in the degradation of GAGs can cause lysosomal storage diseases |
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Antibiotics and Cell Wall syn
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A. Penicillin targets Peptidoglycans which are a component of the bacterial cell wall
B. Bacitracin (can work on euk; so only topical); inhibits peptidoglycan synthesis C. Vancomycin inhibits transfer of a sugar to the peptide in peptidoglycan synthesis |
