FTM 45 - Proteoglycans and Glycoproteins Flashcards
What is a GAG, proteoglycan, and glycoprotein?
Describe the basic composition of a GAG.
Are GAGs typically more positive or negative? Why?
GAGs have strong negative charges from the carboxyl and sulfate groups.
What type of medium do GAGs produce and how? How does the medium help with stuctural integrity?
GAGs produce a gel-like matrix by binding large amounts of water. This matrix is resilient to compression because it just squeezes water out and then reabsorbs it upon relaxation.
What are the four primary functions of GAGs?
What are the GAGs we need to know?
Chondroitin Sulfate
Keratan Sulfate
Dermatan Sulfate
Heparin
Heparan Sulfate
What is the most abundant GAG found in the body and where are they usually found?
Chondroitin Sulfates.
Found in bone, cartilage, ligaments, and the Aorta
On what positions can chondroitin be sulfated?
4 or 6
Things to know about Keratan Sulfates.
Things to know about Dermatain Sulfates
Things to know about heparan sulfate
Things to know about heparin
Why do proteoglycans have a bottle-brush structure? What properties does the structure convey to its medium?
List the major steps of proteoglycan synthesis.
Where does proteoglycan synthesis occur? Where does their aggregation occur?
They are synthesized intracellularly and they aggregate in the ECM.
List the major steps in the synthesis of Glucuronic acid.
List the major steps in the synthesis of amino sugars.
What serves as the central GAG strand for proteoglycan aggregates? How many of these per central strand on average.
Hyaluronic acid (50,000 units)
What are the two primary functions of proteoglycan aggregates?
Shock absorber
Lubricant
What makes hyaluronic acid a unique GAG?
Where is hyaluronic acid commonly found?
Vitreous humor of the eye
Synovial fluid of the joints
Cartilage
Loose connective tissues
What does hyaluronic acid help facilitate?
Cell migration in embryogenesis, morphogenesis, and wound repair
Do glycoproteins and proteoglycans contain mainly protein or sugar?
Glycoproteins are mainly protein
Proteoglycans are mainly sugar
Things to know about glycoprotein structure.
What type of protein are most serum proteins? What is the exception?
Glycoproteins
Albumin
Things to know about mucins
Things to know about blood types and glycoproteins.
What are the primary components of the glycocalyx? What are some of its main functions?
The components of the glycocalyx have many beneficial functions? What are some of their detrimental functions?
How does E. coli adhere to the human body initially?
How does H. pylori adhere to the human body initially?
What is Dolichol-PP? What is it used for?
A lipid containing many isoprene units (a small hydrocarbon) that is bound to the RER membrane. This compound is used to hold a mannose rich oligosaccharide that will later be transferred to an aspargine residue of a protein.
Which proteins will be N-glycosylated?
All proteins that are synthesized by the RER will be N-glycosylated by a mannose rich precursor. This precursor will be modified later
After a protein has been N-glycosylated, what happens to it?
The mannose-rich oligosaccharide begins to carbohydrates trimmed off while still in the RER lumen. This trimming continues in the golgi resulting in the protein becoming a high-mannose glycoprotein or a complex glycoprotein.
How does a protein get sent to a lysosome?
During post-translational modification a specific phosphotransferase which can recognize lysosomal proteins begins the process of N-glycosylating these proteins with mannose 6-P. A mannose 6-P receptor in the golgi will bind to the lysosomal enzyme and package them into vesicles for transport into lysosomes where they will be activated.
What lysosomal storage disease do we need to know? What causes it and what are its symptoms?
I-cell disease
Caused by a deficiency of the phosphotransferase needed to N-glycosylate a lysosomal protein with M6P. This leads to the lysosomal protein being secreted by the cell instead of being sent to the lysosome. Consequently, lysosomes cannot degrade waste molecules and they accumulate, forming inclusion bodies (I-cell).
Which amino acids undergo O-glycosylation and which ones undergo N-glycosylation?
O-glycosylation - serine, threonine, hydroxylysine
N-glycosylation - asparagine and glutamine
What is a key differnce between O and N-glycosylation besides where the sugar is linked?
O-glycosylation involves individual linkage of sugars step by step directly to the protein while N-glycosylation involves the transfer of an oligosaccharide from Dolichol-PP to the protein
