LG 2.4 - Biochemistry of Bone

Question 1

Explain how the structures of glycine and of proline affect peptide backbone flexibility in comparison to other amino acids?

Answer 1

• Proline: the amino acid that most constrains peptide backbone flexibility, because it puts a closed ring in the backbone that allows no rotation around that bond.
• Glycine: the amino acid that least contains peptide backbone flexibility because it has the smallest of all side chains (H atom).

Question 2

What is the amino acid repeat motif of pro collagen and tropocollagen?

Answer 2

• Glycine, proline, hydroxyproline.

Question 3

What is glycine’s role in the tripeptide repeat G-X-Y of the collagen amino acid sequence?

Answer 3

• It constrains the backbone the least, and bonds with prolines on other chains to form the triple helix.

Question 4

Explain why a collagen fibril has a banding patter that repeats every 67 nm?

Answer 4

• ## Hydroxylapatite crystals nucleate within and grow beyond the gap regions of collagen fibrils, thereby cement the tropocollagen building blocks together, further stabilizing collagen fibrils, and contributing to the 67nm banding pattern.