Collagen’s unique blend of amino acids

• ~ 30% of residues are  Glycine • ~ 30 of residues are Proline or Hydroxyproline (HyPro) •  5-hydroxylysine (HyLys) also occurs; a site for glycosylation • Hydroxylation of Pro, Lys is a post-translational modification, requires vitamin C as a reactant • The sequence of collagen bears long stretches of         Gly--Pro/HyPro-X repeats

4-HyPro

3-HyPro

5-HyLys