Collagen

This is the main protein of connective tissue in the bodies of animals. Collagen is found in bones, cartilage, tendons, teeth, skin, cornea of the eye, lungs, liver, blood vessels, and other organs and tissues. It makes up about 25-30% of mammalian proteins. There are 12 types of collagen identified in the human and vertebrate bodies, composed of more than 24 different polypeptide α chains. Combinations of these chains determine the types of collagen. For example, the most common Type I collagen (90% of total collagen mass) is made up of 2 α-1 and 1 α-2 chains. Collagen differs from other proteins in the body in its unique composition of amino acids: Gly accounts for 33% of all amino acids, Pro – 10%, hydroxy-Pro – 10%, and hydroxy-Lys – 1%. The basic structural unit of collagen is tropocollagen, consisting of three left-handed α chains twisted into one right-handed superhelix. These superhelices are connected by cross-linking covalent bonds, forming fibrils.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė