Collagen

Question 1

What is the most abundant protein in our bodies?

Answer 1

Collagen

Question 2

Collagen is made up of how many polypeptides wound around each other to form a rope-like collagen helix?

Answer 2

3

Question 3

What property of collagen keeps it rigid when most other proteins are clumped up in a hydrophobic mess?

Answer 3

Its triple polypeptide helical domain

Question 4

Give 3 examples of fiber forming collagens.

Answer 4

Collagens I, II and III

Question 5

Give an example of a network forming collagen.

Answer 5

Collagen IV

Question 6

Give a collagen specific sequence of amino acids.

Answer 6

Every third residue is a Glycine i.e. X-Y-GLY-Y-X-GLY…

Question 7

Collagen is responsible for:

Answer 7

Structural/functional integrity of our body

Question 8

Collagen self assembles which is followed by stabilization by:

Answer 8

Cross-links - essential for the fiber or network to withstand the physical stresses to which they are exposed.

Question 9

What three things are necessary for a protein to be called a collagen?

Answer 9

3 protein subunits wound around each other in a helix

Repeating sequence of AAs GLY-AA-AA-GLY-AA-AA…etc

Cross-linking of polypeptides for mechanical strength

Question 10

Where do the 3 polypeptides form a collagen triple helix?

Answer 10

Intracellularly before being secreted.

Question 11

What are the two most common AAs found in collagen besides GLY?

Answer 11

Proline and Hydroxyproline

Question 12

Is the center of a collagen helix hydrophillic or hydrophobic?

Answer 12

Hydrophobic

Question 13

If you were to look down the center “barrel” of a simple collagen helix, what atom would find down its length?

Answer 13

Hydrogen

Question 14

One cause of this disease, is a substitution of CYS for GLY in collagen. The strength of collagenous tissues like bone is lowered, leading to multiple fractures.

Answer 14

Osteogenesis Imperfecta

Question 15

Hydroxyproline and hydroxylysine are AAs of collagen formed in a ______ _______ dependent reaction.

Answer 15

Vitamin C

Question 16

Proline + alpha-ketoglutarate and O2 and Vit C (via prolyl hydroxylase)&raquo_space;»> ____________

Answer 16

Hydroxyproline

Question 17

Lysine + Vit C (via lysyl hydroxylase)&raquo_space;»»» __________

Answer 17

Hydroxylysine

Question 18

Scurvy, a collagen deficiency, is caused by an absence of this in one’s diet:

Answer 18

Vitamin C

Question 19

This building block of collagen can be measured in urine to estimate collagen turnover:

Answer 19

Hydroxyproline

Question 20

Hydroxylysine has a special ____ glycosylation in collagen.

Answer 20

O-glycosylation

Question 21

Collagen is synthesized from 3 proline-___ chains, translated into the ER lumen

Answer 21

alpha chains

Question 22

List the 4 steps of procollagen synthesis in the ER/Golgi

Answer 22

1. Synthesis of PRO-alpha chain.
2. Hydroxyation of selected prolines and lysines.
3. Glycosylation of selected hydroxylysines
4. Self-assembly of three PRO-alpha chains into trimeric helix.

Question 23

What ensures that PRO-alpha chains are not frame-shifted and are in the right position (“correct register of GLY-X-Y repeats)” before being wound into a helix?

Answer 23

disulfide bonds that form between globular C-terminal ends

Question 24

On a molecular scale, what causes the symptoms of scurvy?

Answer 24

collagen triple helix does not form because there are not hydroxylated AAs. The hydroxylated AAs raise the melting point of the collagen fibers.
So, not HO-AAs = lower melting point of collagen + normal body temp = degraded/malformed collagen = broken/fragile skin, blisters, ulcers, etc.

Question 25

What must be removed before fibrillar collagens can become mature collagen ready to self-assemble into fibrils and fibers?

Answer 25

Terminal globular domains - those that helped align the 3 strands to form a triple helix.

Question 26

Collagen molecules are covalently cross-linked by this enzyme once they are secreted from the cell.

Answer 26

Lysyl oxidase

Question 27

The covalently bonded cross-link between mature collagen molecules is called a:

Answer 27

Schiff base

Question 28

The strength of tendons to resist pulling forces is due to:

Answer 28

covalent cross-linking between collagen molecules

Question 29

If you do not have proper GLY-X-Y repeats, you will have this disease:

Answer 29

Osteogenesis Imperfecta

Question 30

Failure of proline hydroxylation leads to this disease:

Answer 30

Scurvy

Question 31

Failure of LYS hydroxylation leads to these two diseases:

Answer 31

Scurvy, Ehlers-Danlos Syndrome (many causes)

Question 32

Failure of procollagen to process collagen aggregation leads to these diseases:

Answer 32

Ehlers-Danlos & Dermatosparaxis in cattle

Question 33

Failure of mature collagen to cross-link (no lysyl oxidase) leads to this disease:

Answer 33

Ehlers-Danlos

Question 34

True or False: Collagen degradation is not very highly regulated.

Answer 34

False, it is highly regulated.

Question 35

Degradation of collagen requires activation of this enzyme:

Answer 35

Procollagenase (a special matrix metalloproteinase [MMP])

Question 36

The activity of MMPs is regulated by:

Answer 36

TIMPs

Question 37

Some bacteria, such as genus Clostridium, use this enzyme to destroy collagenous barriers to infection.

Answer 37

MMPs

Question 38

What property of Type IV collagen allows it to form a tetramer network?

Answer 38

the globular ends, that were not removed before the collagen was secreted.

Question 39

Collagen IV is a _______ forming collagen that is a component of basal lamina and other barriers to cells and macromolecules, which self-assemble to form a chain link fence or sievelike structure.

Answer 39

network forming

Question 40

Type IX collagen is a _____-________ collagen that limits growth of fibers, or enhances the interaction of the fiber with extracellular matrix components.

Answer 40

fibril-associated

Question 41

Type VII collagen is part of the anchoring fibril that holds _______ onto underlying connective tissue.

Answer 41

epithelium