lecture 22 - collagen Flashcards
what does collagen form?
forms connective tissue: tendons, cartilage and bone
what is the main function of collagen?
structural integrity
explain the primary structure of collagen
-repetitive aa sequence: (G-X-Y)n
(where X is often pro and Y is often 4-OH-pro)
-composition= 35% gly, 20% pro and 11% ala
-pro subset are hydroxylated, meaning they have an extra OH
-now prolyl hydroxylase
-this is a post-translational modification that increases polarity and adds hbonding capability
explain the secondary structure of collagen
- left handed helix
- 3.3 res/turn
- 9.4 A pitch (much more extended than an alpha helix)
explain the tertiary structure of collagen
same as secondary structure
explain the quaternary structure of collagen
-3 polypeptide chains (left handed helix) wrap around each other in a right handed super helix
-h-bonds between chains, perpendicular to helix axis
(gly is the hbond donor and X is the hbond acceptor)
-~1000 aa/chain (~300 repeats, ~3000A long)
-tighly packed and extended structure
-results in high tensile strength
-several triple-helices pack together into fibrils (which is a higer order structure) which are stabilized by vdW, hbonds and electrostatic interactions.
what allows for tight packing of the quaternary structure?
would other peptides be able to form the conformation without this?
- gly
- individual polypeptides would not form this conformation on their own
- need the hydrophobic packing of 3 chains and the hbonding between 3 chains
what does the 4-OH-Pro provide?
hbonding ability in the supramolecular structure (btwn one triple helices and another)
what catalyzes the hydroxylation of pro?
what does this require?
prolyl 4-hydroxylase which requires vit. C as a cofactor
what is the result of a lack of vit. C?
- reduction in the stability of connective tissue
- e.g. scurvy
