What Is Collagen?

Answer:
The most abundant protein in all mammals is collagen.

Roughly one quarter of the protein in your body is collagen. Collagen is the main protein which makes up connective tissue in the body.

Collagen has a great amount of tensile strength, and it is the main component of the ligaments and tendons. This protein is also responsible for the skin’s elasticity, and wrinkles which come with aging are due to the breakdown and degradation of collagen. Collagen also is found in crystalline form in the cornea of the eyes. Collagen is also used in some plastic surgery procedures, such as lip enhancement.

Collagen has an uncommon amino acid composition. It contains a large amount of glycine and proline, as well as two more amino acids that are not inserted directly by ribosomes. These are hydroxyproline and hydroxylysine. Hydroxyproline makes up a large percentage of the total amount of amino acids. They are derived from proline and lysine in enzyme processes of post translational modification, which requires vitamin C to complete. This process is why vitamin C deficiency can lead to scurvy, which is a disease that can lead to tooth loss and easy bruising which is caused by either a lack of collagen or defective collagen. The white collagen that is the matrix of most of the connective tissue in mammals is made of interwoven fibers made from the protein collagen. These collagen fibers are made up of globular units of the smaller unit of collagen known as tropocollagen. Tropocollagen units will spontaneously arrange themselves under physiological conditions into staggered array structures that are stabilized by many hydrogen and covalent bonds. Tropocollagen units are left handed triple helices where each of the strands is also a right handed helix. Another way to think of tropocollagen is as a coiled coil, where each chain is a left handed helix and the wrapping itself is right handed.

One more of the rare things about collagen is the regular arrangements of amino acids is each of the alpha chains of the collagen units. The sequence usually follows the pattern of Gly-X-Y, where Gly stands for glycine, and the X and Y are for the amino acid residues. X is usually proline, and Y is usually hydroxyproline. Very few other proteins display features this kind of regularity. The resulting structure is referred to as a collagen helix.