L17

Question 1

Define metizoan

Answer 1

Multicellular animals

Question 2

Define tissue and give the 4 types and provide examples for each

Answer 2

• several cells of the same origin come together
  1. epithelial
  2. connective: tendons, ligaments, cartilage
  3. muscular: skeletal, cardiac, smooth
  4. Neural: neuron, neuroglial

Question 3

Define Organ

Answer 3

different tissues working together to form a functionally and anatomically distinct part of a body.

Question 4

What is the ECM

Answer 4

network of proteins and carbs

Question 5

What 4 molecules make up the ECM?

Answer 5

Proteoglycan
Collagen
Elastin
Multiadhesive proteins

Question 6

What is the stroma

Answer 6

ECM + associated cells

Question 7

What is collagen?

Answer 7

is a parallel triple helix (not an Alpha-helix) that has a repetitive sequence with every third residue as glycine. 1050 amino acids long

Question 8

Where is collagen found?

Answer 8

It is the most abundant protein in mammals (~30% by wt), it is in tendons, cartilage, bones, teeth, skin.

Question 9

How many isoforms of collagen?

Answer 9

• 16 known isoforms,

- isoforms I, II, and III make up 90% of collagen

Question 10

What does the core of collagen consist of?

Answer 10

1. repeating
Gly-Pro-HyP
or
2. Gly-X-Pro/HyP
-> X can be any AA, except Trp.

Question 11

Describe the biosynthesis and secretion of collagen

Answer 11

1. Polypeptide synthesis of the Pre-pro-collagen – transported to ER
2. PTM: hydroxylation of some P and K
3. PTM: some glycosylation
4. Form triple helices
   Starts at C-term
5. export across PM
6. Termini clipped off, processed pro-collagen
7. Tropocollagen associate into fibrils
8. cross-links between Lys and Hyl residues

Question 12

Draw the chemical rxn for hydroxyproline formation

Answer 12

Slide 6

Question 13

How is hydroxyproline essential for collagen stability?

Answer 13

1. Inc MT: A peptide w/10 Gly–Pro–Pro repeats will fold to form a collagen triple helix, but the structure melts at 41 °C vs. if the 10 repeats are changed to Gly–Pro–4-Hyp, the melting temperature jumps to 69 °C.
2. Water molecules help to bridge H-bonds between chains

Question 14

How does hydroxyproline essential for collagen stability?

Answer 14

1. Tight packing of Gly, forms hydrophobic core in Collagen

2. Inserting Ala (orange sticks) into Gly position leads to a loss in collagen stability.

Question 15

Draw cross-linking of collagen

Answer 15

1. Peptidyl-lys
   - – lysyl oxidase (deanimates peptidyl-Lys to the corresponding aldehyde) –>
2. Peptidyl-allysine
3. Lysine-norleucin cross link (an aldimine)
4. Pyridinodine

Question 16

Fxn of matrix metalloprotease (MMP)?

Answer 16

Remodelling of collagen/ECM by cleavage

- degrades diff proteins in the ECM

Question 17

Examples of matrix metalloproteases

Answer 17

Collagenases, gelatinases

Question 18

How many different matrix metalloproteases are there? How are they activated?

Answer 18

1. 28 diff MMP

2. MMPs secreted as zymogens and activate each other by cleavage of a propeptide

Question 19

What is the structure of MMPs? Conserved sequence?

Answer 19

1. B-helix stabilized by Ca2+
2. Catalytic Zn2+ and water in active site
3. Conserved sequence: His-Glu-X-X-His-X-X-Gly-X-X-His

Question 20

Draw the typical metallo-protease mechanism

Answer 20

Slide 13

Question 21

How are MMPs regulated?

Answer 21

4 tissue inhibitors of matrix metalloproteases: TIMP1, TIMP2, TIMP3, TIMP4

Question 22

Describe the structure of elastin

Answer 22

1. 750 AA’s in length
2. Forms elastin fibres
3. Nonglycosylated, contains no Hyl, and very little Hyp

Question 23

Draw the mechanism for cross-linking of elastin desmosine

Answer 23

Slide 16