Proteins 3 (Collagen) Flashcards
Which family of srtructurally related proteins is the most abundant protein in mammals, where it is present in most organs?
Collagen
Which protein is the major fibrous element of teeth, skins, bones, cartilage and blood vessels?
Collagen
Where are the polypeptide chains that make up collagen synthesized?
On the rough endoplasmic reticulum (by ribosomes)
What are the two main post translational modifications that happen in the RER and golgi apparatus?
Hydroxylation of amino acid residues
Glycosylation, addition of glucose, galactose
Which amino acid residues are exclusively found in collagen?
Hydroxyproline and Hydroxylysine
Why does vitamin C deficiency cause fragile blood vessels, slow wound healing and skin lesions?
Hyp and Hyl are not synthesised
Why does the hydroxylase require vitamin C?
Hydroxylase has iron ions which need to remain in a reduced state
The antioxidant properties of vitamin C allow this
Vitamin C:
Ascorbic acid
By weeight, what is the range of amount of sugars in collagen?
0.4% to 12%
What is the name for the triple helical structure formed by three collgaen polypeptides coming together?
Procollagen
Which enzymes remove extensions on polpeptide chains of collagen?
Peptidases
What is the repeating unit of collagen polypeptides?
Gly-X-Y
where X is usually proline
and Y is usually Hyp
After secretion, where are extensions of collagen polypeptides removed?
In the extracellular space of connective tissues
At which of the termini do peptidases remove extensions from collagen?
Both of them
The removal of extensions from procollagen forms _
Tropocollagen
How long is each collagen polypeptide chain?
About 1000 residues long
Each collagen polypeptide chain forms a helix with _ residues per turn
3.3
compare to 3.6 in alpha helix
Why might a mutation that replaces glycine residues in collagen disrupt the helical structure?
Only glycine has a side chain small enough for it to fit in to the space at the centre of the helix
What quality of Pro and Hyp confers rigidity on the structure of collagen?
Relative inflexibility
What problem is caused by defective collagen structures?
Brittle bones (osteogenesis imperfect)
How do extension peptides help to align 3 collagen polypeptide chains?
Through the formation of disulfide bonds between cysteine residues
Extensioon peptides prevent premature aggregation of _
Procollagen triple helices within the cell
What properties of collagent fibers imparts strength and rgidity?
Crosslinks between and within tropocollagen molecules
How do tropocollagen molecules aggregate together?
In a head to tail arrangement
Crosslinks between tropocollagen molecules are between _
Lysine and its aldehyde derivative Allysine
What does the enzyme lysyl oxidase catalyse?
The formation of allysine from lysine
