Collagen triple helix hydrogen bonding

Figure 16 Interchain hydrogen bond network in collagen triple helix. The figure was generated using the UCSF Chimera package and coordinates from PDB structure 1QSU.

Ramachandran, G. N., and Chandrasekharan, R. (1968). Interchain hydrogen bonds via bound water molecules in the collagen triple-helix. Biopolymers 6, 1649-1658. 

Figure 2.21. Stabilization of collagen triple helix. The diagram shows hydrogen bonding between the amide hydrogen in position 4 on chain A and the carbonyl oxygen in position 2 on chain B. A second water-mediated hydrogen bond occurs when hydroxyproline is present in position 3 on chain A between the carbonyl oxygen in position 1 on chain A and the amide hydrogen in position 2 on chain B.

Why does impaired hydroxylation have such devastating consequences Collagen synthesized in the absence of ascorbate is less stable than the normal protein. Studies of the thermal stability of synthetic polypeptides have been especially informative. Hydroxyproline stabilizes the collagen triple helix by forming interstrand hydrogen bonds. The abnormal fibers formed by insufficiently hydroxylated collagen contribute to the skin lesions and blood-vessel fragility seen in scurvy. 

Figure 1.31 Cartoon depiction of the right-handed collagen triple helix. Depiction emphasises how three polypeptides in Left-handed Pn helical conformations associate to form the triple helical structure wherein each polypeptide adopts a gentle right-handed rope-like twist in order to maximise stabilising inter-chain hydrogen bond interactions. Structure is also stabilised by a sheath of ordered water molecules of solvation (illustration from Voet, Voet Pratt, 1999 [Wiley], Fig. 6-17).

Collagen forms a triple helix, where three chains of connected amino acids form weak hydrogen bonds between the double-bonded oxygen atoms and the hydrogen atoms attached to the adjacent chain s nitrogens. The three chains then twist together like three cords in a rope. 

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