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
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?
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
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