The major protein (comprising over half of that in mammals) of the white fibers of connective tissue, cartilage, and bone; insoluble in water but can be altered to easily digestible, soluble gelatins by boiling in water, dilute acids, or alkalis. It is high in glycyl,
l-alanyl,
l-prolyl, and
l-4-hydroxyprolyl residues, but is low in sulfur and has no
l-tryptophanyl residues. It comprises a family of genetically distinct molecules all of which have a unique triple helix configuration of three polypeptide subunits known as α-chains; at least 18 types of collagen have been identified, each with a different polypeptide chain.
See also:
collagen fiber.
[G. koila, glue, + -gen, producing]