Focus protein: Collagen
Keeping animals in shape
Illustration from the RCSB Protein Databank.
The collagen triple helix is the most common protein structure in the body. It is found in bones and teeth, tendons, ligaments and cartilage, the walls of arteries, and one of the thin layers of the cornea that protects our eyes. Altogether, around one-third of all the protein in vertebrates is collagen.
Collagen fibrils combine with other materials in the extracellular matrix, which fills the space between cells in different ways in different tissues. In bone, for example, calcium phosphate crystals form in the gaps between collagen fibres to harden it.
Partially degraded collagen from the bones and skin of animals makes gelatine, which is the substance that gives marshmallows and sweets their squishy texture.