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. Contains mostly 4-hydroxyproline. Proline residues at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains. Contains 3-hydroxyproline at a few sites. This modification occurs on the first proline residue in the sequence motif Gly-Pro-Hyp, where Hyp is 4-hydroxyproline. Lysine residues at the third position of the tripeptide repeating unit (G-X-Y) are 5-hydroxylated in some or all of the chains. O-glycosylated on hydroxylated lysine residues. The O-linked glycan consists of a Glc-Gal disaccharide. 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.