Proteoglycans Flashcards
The GAGs in PGs are poly anions or cations?
Anions
What are the component parts of a proteoglycan (PG)?
Core protein, repeating disaccharide, glycosaminoglycan (GAG) made of repeats of an amino sugar and an acid sugar
PGs withstand pressure well because they are:
Hydrated with water and bound Na+ causing a swelling pressure
How is it that Na+ is attracted to GAGs?
GAGs are negatively charged, so they attract +ive charges such as those in Na+
PGs are commonly found in what tissues where resistance to compressive forces would be valuable?
Cartilage
Aggregates of PGs are called:
Aggrecan
________ proteins are the proteins onto which GAG chains are O-glycosidically liked by serine residues to form PGs.
Core proteins
Define GAG.
Repeating disaccharide which forms the “glycan” of proteoglycan.
PGs are distinguished by their variable:
GAG chains. Although each chains is a pure repeating disaccharide, the repeated disaccharide determines the name.
Which GAG exists as a free GAG, not covalently attached to protein like in a proteoglycan, and is not sulfated?
Hyaluronate (hyaluronic acid)
Name 4 GAGs that are covalently attached to proteins through serine and a link trisaccharide, and are sulfated.
Chondroitin sulfate, dermatan sulfate, heparin sulfate, heparin.
Name three tissues in which hyaluronic acid is found.
Cartilage, Synovial fluid, vitreous humor
What is required for link trisaccharides and GAGs to be added to proteins?
(ASP/GLU-X-SER-GLY) forming a serine O-glycosylation recognition sequence.
Link trisaccharides usually link _________ to __________
Proteins to GAGs
What is the last step in PG synthesis?
Sulfation of the GAG, adding negatively charged sulfate groups that will attract H2O and Na+
Name a shock absorbing PG aggregate found in cartilage.
Aggrecan (a hyaluronic acid molecule)
Fibroblast Growth Factor can serve to store ________ __________ to make them readily available for healing and repair when needed (such as after a cartilage tear)
Growth factor
Cell surface and extracellular matrix _______________ aid interactions of cell surface adhesive proteins like integrin and Fibronectin to provide fine tuning of matrix-cell interactions.
Proteoglycans
Because of their capacity for multiple interactions with other proteins, growth factors and cells, __________ can act as an all purpose, reversible glue.
Proteoglycans
Describe the process by which PGs are internalized and catabolized.
Core protein is internalized and can be recycled but the GAG chains are degraded.
Mucopolysaccharidoses are caused by:
Defects in recycling of PGs and mucolipids from the cell surface.
