Proteoglycans And Glycoproteins

Question 1

Glycoproteins:

1. Primarily made of __
2. Exception to 1?
3. Charge of CHO chains
4. Structure
5. Name?

Answer 1

1. Protein
2. Mucin
3. MAY be negatively charged
4. Short chains, branched, no repeating disaccharide units
5. Oligosaccharides

Question 2

Proteoglycans:

1. Primarily made of __
2. Charge of CHO chains
3. Structure
4. Name?
5. Give an example of an important proteoglycan

Answer 2

1. Carbohydrate
2. ALWAYS negatively charged
3. Long chains, unbranched, with repeating disaccharide units
4. Glycosaminglycans (GAGs)
5. Hyaluronic acid

Question 3

The repeating disaccharide unit of GAGs is primarily

Answer 3

[acidic sugar - amino sugar]n

Question 4

GAGs:

Amino sugars can be sulfated on which carbons?

Answer 4

C4 / C6

Question 5

1. What is the old term for GAGs

2. What is the name of the GAG storage diseases

Answer 5

1. Mucopolysaccharides

2. Mucopolysaccharidoses

Question 6

What happens when GAGs are near each other, why?

Answer 6

They repel each other because they are always negatively charged

Question 7

Name an important function of GAGs and 3 places in the body where they are found

Answer 7

Shock absorption/lubrication; found in synovial fluid, vitreous humor, and umbilical cord

Question 8

1. What happens if you compress a GAGs solution?

2. What happens when you release the compression?

Answer 8

1. They lose water and occupies a smaller volume

2. They spring back (reforms the shell of hydration)

Question 9

1. How are the 6 major classes of GAGs recognized? (3 things)
2. All are extracellular except?

Answer 9

1. Monomeric composition, type of glycosidic linkage, and degree/position of sulfation
2. Heparin

Question 10

Chondrotin sulfates:

1. Found in what parts of the body (5)
2. What do they form
3. What is unique about them

Answer 10

1. Cartilage, tendon, bones, ligaments and aorta
2. Form proteoglycan aggregates, often aggregating non-covalently with hyaluronic acid
3. Most abundant GAG in the body

Question 11

Keratan sulfates:

1. What is unique about them
2. Where in the body are they found (3)

Answer 11

1. Only GAG with a simple sugar in its disaccharide unit (galactose)
2. CORNEA, cartilage and bone

Question 12

Dermatan sulfate:

1. Where in the body is it found (3)

Answer 12

1. Skin, blood vessels and heart valves

Question 13

Heparin:

1. Where in the body is it located
2. Serves as __

Answer 13

1. Liver and mast cells (intracellularly)

2. An anticoagulant

Question 14

Heparan sulfate:

1. Difference in the disaccharide units compared to heparin?
2. Where in the body is it found

Answer 14

1. In heparan sulfate, some glucosamines are acetylated and there are fewer sulfate groups
2. Cell surfaces and basement membranes

Question 15

Hyaluronic acid:

1. Where in the body is it found
2. What is its disaccharide unit?
3. What is unique about it (3)

Answer 15

1. Joint and ocular fluids
2. N-acetylglucosamine and glucuronic acid
3. Only GAG with no sulfate, not covalently attached to protein, and only GAG also found in bacteria

Question 16

Structure of proteoglycans:

1. Chains are separated by __
2. What kind of structure does this give them?

Answer 16

1. Charge repulsion

2. Bottle brush

Question 17

What enzyme does venom contain

What does this enzyme do?

Answer 17

Hyaluronidase

Breaks through basement membrane so venom can enter

Question 18

Synthesis of acidic sugars:

1. What is the difference between D-glucuronic acid and L-iduronic acid?
2. What does GAG synthesis require? What else is this important for?

Answer 18

1. D-glucuronic acid is derived from glucose; L-iduronic acid is its carbon-5 epimer
2. UDP-glucuronic acid; making indirect bilirubin into direct bilirubin (conjugation)

Question 19

Synthesis of core protein:

1. Location?
2. What happens as it moves through the ER

Answer 19

1. Synthesized on and enters the rER

2. It is glycosylated by membrane-bound transferases

Question 20

Synthesis of the carbohydrate chain:

1. Begins by synthesis of ?
2. Linkage starts with transfer of __ to __ by which enzyme?
3. What happens next?

Answer 20

1. Linkage region on the core protein
2. Xylose to the -OH of a serine or threonine; xylosyltransferase
3. 2 galactose molecules are added to make the trihexoside linker (protein-xylose-gal-gal), followed by addition of repeating disaccharide (alternating acidic and amino sugars)

Question 21

Addition of sulfate groups:

1. Sulfation only occurs after __
2. Sulfate is carried on ?
3. What catalyzes sulfation at specific sites

Answer 21

1. After the monosaccharide has been incorporated into the growing chain
2. 3’-phosphoadenosyl-5’-phosphosulfate (PAPS)
3. Sulfotransferases

Question 22

Chondrodystrophies:

3 autosomal recessive disorders known from different mutations in DTDST gene coding for a ___

Answer 22

Sulfate transporter

Question 23

Linkage region is formed from __

Linkage region is required to __

Answer 23

Multiple serine residues

To elongate GAGs

Question 24

Mucopolysaccharidoses:

1. First 2 disorders known called __
2. All are autosomal __ disorders except for __

Answer 24

1. Gargoylism (distinct facial features)

2. Recessive; hunter syndrome (X-linked)

Question 25

Hurler syndrome: 1. AKA 2. Deficiency in what enzyme 3. Symptoms 4. What about this syndrome leads to early death? 5. Treatment * 6. Affects degradation of what 2 things?

Answer 25

1. MPS IH 2. L-iduronidase deficiency 3. Corneal clouding, coarse facial features, mental retardation 4. Deposition in coronary arteries 5. Enzyme replacement/bone marrow graft (before 18 months) 6. Heparan and dermatan sulfates

Question 26

Hunter syndrome: 1. AKA 2. Deficiency in which enzyme? 3. Symptoms ? 4. Affects degradation of what 2 things?

Answer 26

1. MPS II 2. Iduronate sulfatase deficiency 3. Macrocephaly, hepatosplenomegaly, mild to severe mental retardation, NO corneal clouding 4. Heparan and dermatan sulfates

Question 27

Glycoproteins: 1. Location in the cell 2. Function in the cell

Answer 27

1. Membrane proteins, cytoskeletal proteins, receptors, and extracellular proteins 2. Antibodies, hormones, collagen, enzymes

Question 28

Sugar chains are carriers of ?

Answer 28

Biological information

Question 29

How carbohydrates linked to the protein component ?

Answer 29

Through either O-glycosidic or N-glycosidic bonds

Question 30

1. The N-glycosidic linkage is between? | 2. The O-glycosidic linkage is to ?

Answer 30

1. Carbohydrate and asparagine | 2. To the -OH of serine, threonine, or hydroxylysine

Question 31

1. What is the carbohydrate that is directly attached to the protein in N-linked glycoproteins? 2. In O-linked glycoproteins?

Answer 31

1. N-Acetyl D-Glucosamine | 2. N-Acetyl D-Galactosamine

Question 32

What must the sequence of asparagine at the site of glycosylation be?

Answer 32

Asn-X-Ser (Thr)

Question 33

Biosynthesis of N-linked glycoprotein: 1. What is the initial oligosaccharide chain? 2. Where is it synthesized? 3. Then it is transferred to where? By what enzyme? 4. Purpose of the 3 glucoses that make up the linkage region (2)

Answer 33

1. Glc3Man9GlcNAc2 2. Dolichol (lipid carrier) 3. To an asparagine residue on the protein by oligosaccharyl transferase 4. To help oligosaccharide transfer from lipid to protein and protein folding

Question 34

What is the precursor for making dolichol?

Answer 34

FPP (farynseal pyrophosphate)

Question 35

Biosynthesis of O-linked glycoprotein: 1. Occurs post-translationally by stepwise addition of __ ;where? 2. What is not involved 3. What is the first sugar to be transferred from UDP? Where is it transferred to? 4. Addition of a galactose and then sialic acid forms?

Answer 35

1. Sugars in the golgi apparatus 2. No lipid carriers are involved 3. GalNAc transferred to serine or threonine residues on a protein 4. The final trisaccharide sequence on a mucin

Question 36

Lectins: 1. Include __ 2. Function 3. 2 of these chaperones? 4. What do they recognize?

Answer 36

1. Chaperone proteins 2. Assist in protein folding 3. Calreticulin and calnexin 4. High-mannose oligosaccharides with a single glucose remaining on their structure

Question 37

Besides protein folding, what is another function of oligosaccharide chains of glycoproteins? What reduces the stability of these proteins?

Answer 37

Increase the solubility of the proteins and their stability in adverse conditions Removal of the carbohydrate

Question 38

1. N-linked glycoproteins are frequently present where? 2. Lectin-cell membrane bound carb interactions provides for 3. Key factor in what 4 processes

Answer 38

1. At the cell surface 2. Specific cell recognition 3. Fertilization, inflammation, development and differentiation

Question 39

HIV gains entry into the immune system cells by attaching to what 2 receptors?

Answer 39

CXCR4 and CCR5 receptors on the cell surface

Question 40

The malarial parasite plasmodium vivax binds to __

Answer 40

The erythrocyte chemokine receptor known as the Duffy blood group antigen

Question 41

1. Most of the hydrolytic enzymes present in the lysosomes are what type of glycoproteins? 2. Enzymes destined for the lysosomes have which type of residue? 3. What receptor are these structures recognized by?

Answer 41

1. N-linked 2. A phosphate group attached to the terminal mannose residue 3. Man-6-P receptor

Question 42

I cell disease: 1. Deficiency of the enzyme required for ? 2. Connective tissue cells in patients with I cell disease contain large inclusions of? * 3. Clinical presentation

Answer 42

1. Mannose phosphorylation 2. GAGs and glycolipids 3. Mental retardation, skeletal deformities, growth retardation, and death by age 5-7

Question 43

1. Mannose-6-phosphate residues are recognized by specific receptors where? 2. In absence of these receptors, what happens to the hydrolytic enzymes?

Answer 43

1. In the golgi apparatus | 2. They are secreted in the ECM and body fluids instead of being dispatched to the lysosomes

Question 44

What will the urine contain in someone with I cell disease?

Answer 44

High concentration of lysosomal enzymes in the urine