Collagen Synthesis Flashcards
In collagen, what are the X and Y amino acids most often?
Proline- X
Hydroxylisine/Hydroxyproline- Y
How many alpha chains are present in collagen?
3
What formation of chains does collagen form?
Triple helix
In collagen, which is every 3rd amino acid?
Glycine
Which types of collagen, out of I, II, III, form fibrils and which form fibres?
All 3 form fibrils
Only type I and II form fibres
Characteristics of type I collagen and where it’s found
High tensile strength
Bone, skin, tendons, BV’s
Characteristics of type II collagen and where it’s found
Cartilagenous
Don’t form fibres
Forms elastic and hyaline cartilage
Name and characteristics of type III collagen and where it’s found
Reticullin
Forms fibres
Skin, BV’s, lymphatic system
What is the name of collagen when it is initially synthesised?
Preprocollagen
Where is collagen precursor synthesised and secreted from?
Fibroblasts
Is the signal sequence on collagen precursor cleaved or retained? If so by what?
Cleaved
Signal peptidase
After cleavage of signal peptide, what is collagen precursor chains called?
Pro α Chains
Why is it important that the collagen chains are hydroxylated?
More OH- groups
TF more H bonds form
TF stronger structure
What modifications occur to collagen in the RER? (In brief)
Hydroxylation (of selected proline + lysine)
Addition of Galactose
N-linked glycosylation
Where does O linked glycosylation of collagen occur?
Golgi body
What is the final thing that happens to collagen in RER, before exocytosis?
Chains align and disulphide bonds form
Forms a triple helix
What is N-linked glycosylation?
Where a sugar (glucose) is linked onto a chain by forming a bond with the nitrogen in the sugar ring
What is O-linked glycosylation?
Where sugar (glucose) is added to chain by forming a bond with the oxygen present in the sugar
Which residues in collagen α chains are selectively hydroxylated? What are they then called?
Proline- Hydroxyproline
Lysine- hydroxylysine
What enzyme catalyses hydroxylation in collagen synthesis?
Prolyl hydroxylase
Which enzyme catalyses the formation of covalent cross link between collagen fibrils?
Lysyl Oxidase
What co-factors are required for the enzyme that catalyses hydroxylation of collagen residues? Name the enzyme too
Prolyl hydroxylase
Vitamin C
Fe2+ ions
What is the general/basic structure of alpha collagen chains?
Glycine-X-Y
What is tropocollagen?
Collagen FIBRILS that have had their N&C terminal propeptides removed?
Once finished in the Golgi, what happens to procollagen?
Transported out of Golgi by transport vesicle
N&C terminal peptides removed
To form tropocollagen
Collagen FIBRILS aggregate to form FIBRES
Lysyl oxidase catalyses formation of covalent bonds
Which residues are selectively N-linked glycosylated and have galactose added to?
Hydrolysine
Proline
Which enzyme catalyses the removal of N&C terminal propeptides?
Procollagen peptidase
What modification to collagen occurs in the Golgi?
O-linked glycosylation
Once tropocollagen has formed, what happens?
Lysyl oxidase catalyses formation of covalent cross links between collagen FIBRILS to form collagen FIBRES
Which enzyme catalyses the formation of covalent cross links between collagen fibrils forming collagen fibres?
Lysyl oxidase
What does CHANDPORC stand for?
Cleavage, hydroxylation, addition of galactose, n-linked glycosylation, disulphide bond formation, procollagen, o-linked glycosylation, removal of N + C propeptides chains, covalent bond formation
