Collagen

Collagen is the principal protein of the skin, tendons, cartilage, bone and connective tissue.

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The major protein (comprising over half of that in mammals) of the white fibers of connective tissue, cartilage, and bone, that is 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 13 types of c. have been identified, each with a different polypeptide chain. SEE ALSO: c. fiber. SYN: ossein, osseine, ostein, osteine. [G. koila, glue, + -gen, producing]

- type I c. the most abundant c., which forms large well-organized fibrils having high tensile strength.

- type II c. c. unique to cartilage, nucleus pulposis, notochord, and vitreous body; it forms as thin highly glycosylated fibrils.

- type III c. c. characteristic of reticular fibers.

- type IV c. a less distinctly fibrillar form of c. characteristic of basement membranes.

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col·la·gen 'käl-ə-jən n an insoluble fibrous protein of vertebrates that is the chief constituent of the fibrils of connective tissue (as in skin and tendons) and of the organic substance of bones and yields gelatin and glue on prolonged heating with water

col·la·gen·ic .käl-ə-'jen-ik adj

col·lag·e·nous kə-'laj-ə-nəs adj

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n.

a protein that is the principal constituent of white fibrous connective tissue (as occurs in tendons). Collagen is also found in skin, bone, cartilage, and ligaments. It is relatively inelastic but has a high tensile strength.

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col·la·gen (kolґə-jən) [Gr. kolla glue + -gen] any of a family of extracellular, closely related proteins occurring as a major component of connective tissue, giving it strength and flexibility. At least 25 types exist, each composed of tropocollagen (q.v.) units that share a common triple-helical shape but vary in composition between types, with the types being localized to different tissues, stages, or functions. In some types, including the most common, Type I, the tropocollagen rods associate to form fibrils or fibers; in other types the rods are not fibrillar but are associated with fibrillar collagens, while in others they form nonfibrillar, nonperiodic, but structured networks. Collagen is converted to gelatin by boiling. See also under disease, fiber, and fibril.