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collagen
Function:
- main protein of connective tissue in animals
- tough bundles of collagen (collagen fibers) are a major component of extracellular matrix
- great tensile strength
- along with soft keratin, give skin strength & elasticity
- collagen gives bone its elasticity & contributes to fracture resistance.
- strengthens blood vessels
- role in tissue development
Structure:
- long, fibrous structural protein with triple helical structure, known as the Madras helix.
- tropocollagen or collage subunit is a rod about 300 nm long & 1.5 nm in diameter, made up of three polypeptide strands, each of which is a left-handed helix#
- the 3 left-handed helices are twisted together into a right-handed coiled-coil, stabilized by hydrogen bonds.
- tropocollagen subunits spontaneously self-assemble, with regularly staggered ends, into even larger arrays in the extracellular matrix of tissue
- some covalent crosslinking occurs within the triple helices
- variable amount of covalent crosslinking between tropocollagen helices
- tropocollagen from young animals can be extracted because it is not yet fully crosslinked
- a distinctive feature of collagen is the regular arrangement of amino acid residues in each of the 3 chains of collagen
- repeats of Gly-X-Pro or Gly-X-Hyp, where X may any amino acid residues
- in collagen, Gly is required at every 3rd position because the assembly of the triple helix puts this residue at the interior (axis) of the helix, where there is no space for a larger side group
- the rings of the Pro & Hyp must point outward
- Pro & Hyp thermally stabilize the triple helix, Hyp more so than Pro
- in bone, entire collagen triple helices lie in a parallel, staggered array
- 40 nm gaps between the ends of the tropocollagen subunits probably serve as nucleation sites for the deposition of long, hard, fine crystals of the mineral component, hydroxyapatite
- in this way that certain types of cartilage turn into bone
- collagen fibrils are collagen molecules packed into an organized overlapping bundle
- collagen fibers are bundles of fibrils.
# alpha helix is right-handed
Compartment:
- extracellular matrix
- also found inside certain cells
Expression:
- most abundant protein in mammals, comprises about 25% of total protein content
- 75% of the dry weight of skin tissue
- main component of fascia, cartilage, ligaments, tendons, bone & teeth
- present in the cornea & lens of the eye in crystalline form
formation of collagen:
- see collagen type-1
Pathology:
- degradation leads to wrinkles that accompany skin aging
- scurvy is associated with defective collagen synthesis & weakened connective tissue
- in connective tissue diseases collagen fibers are destroyed with inflammation of surrounding tissues
- deposition of excess collagen occurs in scleroderma
- bacteria & viruses have virulence factors which destroy collagen or interfere with its production
Pharmacology:
- used in cosmetic surgery & burns surgery
Uses:
- when partially hydrolyzed, the three tropocollagen strands separate into globular, random coils, producing gelatin
Interactions
molecular events
Related
collagenase
procollagen+collagen in fibroblasts
Specific
activated collagen
Collagen Topical
collagen type-1
collagen type-2
collagen type-3
collagen type-4
collagen type-5
collagen type-6
collagen type-7
collagen type-8 (endothelial collagen)
collagen type-9 (FACIT collagen)
collagen type-10
collagen type-11
collagen type-12
collagen type-13
General
matrix protein
multisubunit protein
Properties
COMPARTMENT: extracellular matrix
References
- Wikipedia, collagen entry
http://en.wikipedia.org/wiki/collagen
- Di Lullo GA et al
Mapping the ligand-binding sites and disease-associated
mutations on the most abundant protein in the human, type I
collagen.
J Biol Chem. 2002 Feb 8;277(6):4223-31. Epub 2001 Nov 9.
PMID: 11704682
Component-of
ascorbate/collagen
macromolecular complex