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Collagen
Exploring the Structure
A special amino acid sequence makes the tight collagen triple helix
particularly stable. Every third amino acid is a glycine, and many of the
remaining amino acids are proline or hydroxyproline. A classic triple helix
is shown here, and may be viewed in the PDB file 1cag. Notice how
the glycine forms a tiny elbow packed inside the helix, and notice how the
proline and hydroxyproline smoothly bend the chain back around the helix.
In this structure, the researchers placed a larger alanine amino acid in the
position normally occupied by glycine, showing that it crowds the
neighboring chains.
This collagen helix contains a segment of human collagen, and
may be viewed in the PDB file 1bkv. Notice that the top half is very
uniform, where the sequence is the ideal mixture of glycine and prolines. At
the bottom, the helix is less regular, because many different amino acids are
placed between the equally-spaced glycines.
These illustrations were created in RasMol. You can create similar pictures by clicking on the PDB codes above and then picking "View Structure".
Next:Ropes and Ladders
Previous:Your Most Plentiful Protein
Last changed by: A.Honegger,