Protein Targetting Flashcards
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?
Tropocollagen
3 polypeptide alpha chains
Triple helix
Glycine in every third position
What does collagen structure mean for collagen?
It is non-extensible
Non-compressible
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?
- Synthesis and then entry into Lumen of rough ER
- Cleavage of signal peptide
- Hydroxylation of selected proline and lysine residues
- Addition of N-linked Oligosaccharides
- Addition of Galactose to hydroxylysine residues
- chain alignment and formation of disulfide bonds
- formation of triple helical pro collagen from C- to N-terminus
- completion of O linked oligosaccharide chains by addition of glucose
- transport vesicle
- Exocytosis
- Removal of N- and C- terminus propeptides
- 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?
Extracellular
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
