BCHM- Tropocollagen

  1. What are the two phases of nano-composite of bone?
    • Organic
    • Mineral
  2. What consists of organic phase of bone?
    Collagen- makes bone flexible, ductile and tough
  3. What consists mineral phase of bone?
    Hydroxyapatite crystals- makes bones rigid, stiff and hard
  4. What is collagen?
    • Most abundant animal protein
    • Organic phase of bone
    • Major component of connective tissue
  5. What is tropocollagen?
    The molecular component/ building block of collagen fibril – three peptide chains coiled around each other
  6. What is the amino acid sequence of tropocollagen peptide?
    3-amino acid repeating motif of Glycine-Proline-Proline, or GXY
  7. What does it mean that Glycine is conserved in tropocollagen peptide?
    100% of the time there Glycine will be in the first amino acid of the repeating GXY motif
  8. Where in the cell is this repeating motif made?
    Ribosome during translation
  9. Where in the cell is the amino acid modified?
    Hydroxylation occurs in the endoplasmic reticulum
  10. What is the organization of tropocollagen?
    Three collagen peptides, each with 1000 amino acids length, wrap together to form the triple helical building block of collagen
  11. How many repeats in the tropocollagen amino acid sequence motif?
    350 times
  12. Which amino acid donates the H-bond in tropocollagen?
    Amino acids at X or Y positions that are not proline or hydroxyproline
  13. What is the most common cause of osteogenesis imperfecta?
    Mutation at the glycine position
  14. Why is glycine completely conserved?
    Only glycine has a sidechain small enough to pack into the core of the helix
  15. What exists in the gaps between tropocollagen?
    Hydroxyapatite mortar
  16. Describe what happens to the tropocollagen peptide in the ER
    • Preprocollagen peptide gets hydroxylated at proline/lysin, then glycosylation occurse of the hydroxylysine
    • Helices wrap around the hydroxylated and glycosylated residues forming the triple helix
  17. How many tripeptide repeats per helical turn?
  18. How are tropocollagen molecules packed?
    • In a staggered pattern to form long, wide fibrils.
    • Repeats every 67 nm
  19. Which collagen type(s) are associated with bone
    Types I, II, III
  20. Which gene mutations result in osteogenesis imperfecta
    COL1A1 or COL1A2
  21. Substitution of which amino acid at the glycine position would cause less severe form of osteogenesis imperfecta?
    Alanine, the next smallest AA other than glycine
  22. What is an co-enzyme required for prolylhdyroxylase to work?
    Vitamin C
  23. What does allysine mean?
    Post-translational modification of lysin by lysyl oxidase which replaces the side chain amine with aldehyde
  24. What is a treatment for scurvy?
    Take vitamin C
  25. What is scruvy?
    Chronic vitamin C deficiency
Card Set
BCHM- Tropocollagen
NMSK Exam 2 Bchm Tropocollagen