Which amino acid is primarily involved in the cross-linking of collagen?

Collagen is a vital structural protein found in various connective tissues in the body, and its strength and stability are significantly enhanced by cross-linking between collagen fibers. This cross-linking is primarily facilitated by the amino acid lysine. Specifically, lysine residues can undergo post-translational modifications to form covalent bonds with other lysine or hydroxylysine residues. These cross-links contribute to the tensile strength and stability of the collagen structure, making lysine critical for maintaining the integrity of tissues such as skin, tendons, and cartilage.

While proline and glycine are also important components of collagen—proline being involved in forming the helical structure and glycine being the most abundant amino acid in collagen—they do not play the primary role in cross-linking. Arginine, although it has distinct biological functions, is not directly involved in collagen cross-linking. Therefore, lysine is recognized as the key amino acid involved in this process, providing the necessary links to stabilize and strengthen the collagen matrix.