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Flashcards in Protein Targetting Deck (15):

What is a collagen?

The most abundant protein in the body
In connective tissue


Where is collagen synthesised?

Secreted protein produced by fibroblasts in connective tissue


What is the basic structure of collagen?

3 polypeptide alpha chains
Triple helix
Glycine in every third position


What does collagen structure mean for collagen?

It is non-extensible
High tensile strength


Why is glycine important in collagen?

It is the only amino acid with a side chain small enough to fit in the middle of the helix


What is mainly in the X and Y positions of collagen?

Proline and hydroxyproline


What bonds connect the three alpha chains?

Hydrogen bonds


What is type I collagen and where is it found?

2 alpha I (I) chains and 1 alpha II (I)
Skin, tendons, bone
90% of all collagen


What is type II collagen and where is it found?

3 Alpha I (II)
Cartilage and intervertebral discs


How is collagen synthesised?

1. Synthesis and then entry into Lumen of rough ER
2. Cleavage of signal peptide
3. Hydroxylation of selected proline and lysine residues
4. Addition of N-linked Oligosaccharides
5. Addition of Galactose to hydroxylysine residues
6. chain alignment and formation of disulfide bonds
7. formation of triple helical pro collagen from C- to N-terminus
8. completion of O linked oligosaccharide chains by addition of glucose
9. transport vesicle
10. Exocytosis
11. Removal of N- and C- terminus propeptides
12. Lateral association of collagen molecules followed by coolant cross linking
13- Aggregation of fibrils


What is Prolyl Hydroxylase?

Allows increased Hydrogen bonding to stabilise triple helix
Requires Vitamin C and Fe2+ for activity


What is Scurvy due to?

Lack of vitamin C so Prolyl Hydroxylase will not work so weak tropocollagen triple helix


What is Lysyl Oxidase?

Requires Vitamin B6 and Cu2+ ions for activity
Forms covalent cross-links


Why is Tropocollagen secreted before final processing occurs?

Too large and would destroy the cell if occurred inside the cell


What is EDS?

Ethlers-Danlos Syndrome
Mutation in the Collagen type V or Lysyl Oxidase deficiency