Glycoconjugates Flashcards
What are proteoglycans?
Sugars attached to the serine residues of a simple protein core
What do the sugars on proteoglycans do?
Interact with the water and form a gel
What do proteoglycans do?
Fill space and have biological activity. They can regulate the activity of ECM proteins, or act as growth factors or protease inhibitors
Are proteoglycans attached to the membrane or soluble?
Can be either
What do membrane attached proteoglycans do?
Regulate the movement of large molecules
What does heparan sulfate do?
Is an anticoagulant. It binds to anti-thrombin with its NS domains, which then changes the conformation and binds to blood clotting factor Xa to prevent clotting
Where are aggregate proteoglycans found?
Cartilage
How big are aggregate proteoglycans? What are they made of?
Occupy the same space as a bacterial cell. Made with a hyaluronate with aggrecan proteins coming out the sides
What do aggregate proteoglycans do?
They associate with collagen and provide shock absorption
What is the difference between a proteoglycan and a glycoprotein?
Proteoglycans have GAGs attached to simple protein cores, and glycoproteins have more complex proteins with short, branched oligosaccharides attached to them
What are the sugars attached to in glycoproteins?
To the oxygen in Ser or Thr, or to the N in Asn
Are O-linkages or N-linkages more common in glycoproteins?
N-linkages
Where are glycoproteins made?
The endomembrane system
What is dolichol phosphate?
A lipid that is involved in getting sugars into the ER. Sugars branches are assembled outside then dolichol phosphate flips into the ER lumen and the sugars are moved to the protein
How are the sugar branches built for glycoproteins?
They’re assembled in the cytosol on dolichol phosphate. The sugars are activated as UDP-sugars before they’re attached to the chain and the UDP act as a leaving group
