Type I collagen is a member of group I collagen (fibrillar forming collagen). Trimers of one alpha 2(I) and two alpha 1(I) chains. Forms the fibrils of tendon, ligaments and bones. In bones, the fibrils are mineralized with calcium hydroxyapatite. Prolines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains. This protein sequence was reconstructed from 13,800 and 160,000 to 600,000 year old bones. The tryptic peptides required multiple purification steps in order to eliminate contaminants and to increase the concentration of peptidic material. Belongs to the fibrillar collagen family.