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MBOD Week 15 > Collagen > Flashcards

Collagen Flashcards

1
Q

T or F: collagen is an integral membrane protein.

A

False, it is located completely outside of cells

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2
Q

What sequence is common to all types of collagen?

A

Gly-X-Y sequence

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3
Q

What type of proteins degrade collagen?

A

Metalloproteinases

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4
Q

What is primary structural element of connective tissue?

A

Collagen

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5
Q

T or F: collagen undergoes minimal amounts of post translational processing

A

False, Collagen is highly post translationally processed

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6
Q

Type I collagen

  • Form
  • Where
A

Form:
Fibrillar (fiber form)

Where:
Bone, Skin, Tendon, Cornea, Many others

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7
Q

Type II collagen

  • Form
  • Where
A

Form:
Fibrillar

Where:
Cartilage, Vitreous of eye

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8
Q

Type III

  • Form
  • Where
A

Form:

Skin, Blood vessels, many other

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9
Q

Type IV

  • Form
  • Where
A

Form:
Network

Where:
Basal Lamina Sheets

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10
Q

Type V

  • Form
  • Where
A

Form:
Fibrillar

Where:
Bone, Skin, Tendon, Cornea, Many others

***Note: this is the same as type I

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11
Q

Type VIII

  • Form
  • Where
A

Form:
Network

Where:
Endothelial Lining, cornea

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12
Q

What features are common to all collagen regardless of tissue type?

  • structure
  • sequence
  • Post-Translational Modifications
A

Structure:
- 3 domains wound around each other into a triple helix

Sequence:
- Each subunit contains a Gly-X-Y repeating sequence

PTMs:
- Hydroxylation of proline and lysine

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13
Q

T or F: a single collagen fibril contains many collagen strands

A

True

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14
Q

End to end aggregation of small fibrils form longer fibrils that aggregate to form ____________.

A

Fibers, collagen fibers self assemble from collagen subunits

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15
Q

T or F: different forms of collagen are genetically distinct

A

True, many different collagen genes encode for different types

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16
Q

What proteins commonly fill the x, y positions in Gly-X-Y.

A
  • Hydroxyproline (HYP, and PRO)
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17
Q

Why is glycine nesessary at every 3rd amino acid in collagen?

A
  • is H for an R group is the only thing small enough to fit in the triple helix
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18
Q

What is the result of changing gly to cys in the collagen sequence Gly-X-Y?
- Resultant disease

A
  • Cysteine has a larger side chain and puts a bulge in the collagen
  • This weakens the collagen
  • Osteogenesis imperfecta results (aka brittle bone disease)

**Normally this is a small defect but in collagen this glycine is vital

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19
Q

What it is needed for production of hydroxyproline and hydroxylysine needed for collagen formation?
- what does a deficiency result in?

A
  • Vitamin C

- Vitamin C deficiency leads to scurvy

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20
Q

What enzyme is uses vitamin C as a cofactor?

A
  • Prolyl Hydroxylase enzyme
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21
Q

What are the substrates and products of prolyl hydroxylase?

- Coefactors

A

Substrates:
Proline + alpha KG + O2

Products:
Hydroxyproline + Succinate + CO2

Cofactor:
VITAMIN C

22
Q

Lysyl Hydroxylase

  • Reaction
  • Substrates
  • Products
  • Coefactors
A
  • make hydroxylysine

Substrate:
Lysine

Product:
Hydroxylysine

Cofactor:
Vitamin C

23
Q

What addition can be made to hydroxylysine?

***this is important

A

It can be O-glycosylate for collagen specific glycosylation

24
Q

Slow wound healing and bleeding of gums and lips are symptoms of what disease related to collagen?

A
  • Scurvy, resulting from Vitamin C deficiency

- Scurvy results from lack of Hyroxyproline and Hydroxylysine

25
Q

T or F: hydroxyproline and hydroxylysine are essential to collagen formation

A

True, scruvy is the result of not having these residues

26
Q

Why would you measure someone’s urine hydroxyproline levels?

A
  • It tells you about bone turnover

***note: hydroxyproline is peed out because it is post-translationally modified and can’t be reused

27
Q

What would you expect urine hydroxyproline levels to be like in a patient that has scruvy.

A

Levels will likely be LOW because they lack the appropriate enzymes to make it

28
Q

Why shouldn’t you eat jellow before a hydroxyproline urine test?

A

**Don’t eat jello before one of these tests because it contains collagen and will artificially raise your hydroxyproline levels

29
Q

7 steps of collagen synth.

A
  1. Synthesis of Pro-alpha chain
  2. Hydroxylation of Selected Prolines and lysines
  3. Glycosylation of selected hydroxylysines
  4. Self-Assembly of 3 pro-alpha chains
  5. Procollagen Triple Helix Formation
  6. Secretion
  7. Cleavage of Pro-Peptides
30
Q

Why does lack of hydroxylation causes the effects seen in scurvy?

A
  • Collagen is destabilized and has a lower melting temperature
  • Once dissociated the chains are simply degraded
31
Q

What differentiates Procollagen from collagen?

- what is the importance of this difference?

A

Procollagen:
- Contains GLOBULAR portions

Purpose of Globular parts:
- help align the 3 strands into a triple helix

32
Q

T or F: the globular domains must be removed from procollagen to form collagen which can assemble into fibrils and fibers

A

True

33
Q

What happens if the globular domains are not removed from the procollagen protein?

A

Dermatosparaxis:

  • Fragile Skin
  • Abnormally elastic Skin and Tissues

**Skin loss in cattle and sheep

34
Q

Why does presence of globular domains on procollagen cause skin to be brittle?

A
  • Collagen needs its ends to be free so that it can bind to other collagens and form large strands
35
Q

After collagen is assembled what allows for cross linking between strands?

  • enzyme
  • residues
A
  1. Lysyl Oxidase (not hydroxylase) form ALDEHYDES of lysine and hydroxylysine
  2. Schiff Base is formed
36
Q

Issues in what 3 areas of collagen formation lead to all of the diseases observed?

A
  1. Biosythesis
  2. Procollagen processing
  3. Crosslinking
37
Q

Where does translation of collagen polypeptides typically occur?

A

RER

38
Q

What causes Scurvy?

A

Lack of Vit C, coefactor needed for hydroxylation of proline and lysine

39
Q

What causes Ehlers-Danlos VI?

A
  • Lysyl Hydroxylase Deficiency

**so you still have your hydroxyprolines

40
Q

What do you need procollagen domains?

- why is it bad if they are never cleaved?

A
  • Needed for proper alignment

- Must get rid of so that fiber formation can happen

41
Q

Ehlers-Danlos VII

  • Defect
  • What part of collagen formation is messed up?
A

N-propetidase defect

  • Globular ends (procollgen domains) are not cleaved
42
Q

Ehlers-Danlos IX

  • Defect
  • What part of collagen formation is messed up?
A
  • Lysyl Oxidase deficient

- No Allysine formation so Schiff bases and therefore cross-links can’t be formed

43
Q

What do lathrogens do?

- effect?

A
  • Inhibit Lysyl Oxidase

- This mimics the effects of Ehlers-Danlos (IX)

44
Q

Metalloproteinases (MMP)

  • Function
  • procollagenase
  • inhibitor
A
  • Break Down Collagen

Procollagenase:
- activates the MMP

Inhibitor:
TIMPs

45
Q

What physiologic processes involve metalloproteinases (MMP)?

A
  • Tissue Development
  • Cancer Metastasis
  • Wound Healing
46
Q

T or F: globular ends are maintained in Type IV collagen

A

True, allows it to form a tetramer

**Note: Type IV collagen needed to form a scaffold for the basal lamina

47
Q

Besides type IV collagen, what other type maintains its globular domain?

A

Type IX

48
Q

What is located at the globular end of Type IX collagen?

- what type of collagen is Type IX typically associated with?

A

a GAG chain

  • Type II
49
Q

What is the relationship between type II and Type IX collagen?

A
  • Type II fiber size is regulated by type IX collagen

ALSO, GAG components of Type IX can interact with other collagens

50
Q

What forms the sievelike structure of basal laminae?

A
  • Networks Formed by Type IV collagen
51
Q

What is the job of fibril associated collagens?

- example?

A

Coat other collagens to:

  • Limit Growth of the Fiber
  • Enhance interaction of fiber with ECM
52
Q

What collagen has the job of anchoring fibril to hold epithelia onto underlying CT?

A

Type VII

MBOD Week 15 (7 decks)

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