Structural Proteins

Collagen

Collagen is the most abundant mammalian protein and the main component of connective tissues. Typically collagen is first synthesized as individual glycine-rich preprocollagen monomeric strands from the ribosomes in the rough endoplasmic reticulum (RER). After transport to the lumen of the RER signal peptides are cleaved to yield procollagen. Lysine and proline are hydroxylated and glycosylated in the lumen and a helix composed of three peptides is formed. It is then transported to the Golgi and excreted from the cell by exocytosis. Procollagen's propetides are then removed to yield tropocollagen which may join together to form fibrils. The "collagen type" designations of Bornstein and Traub is determined by the peptide composition of the triple helix.

Collagen Type specific diagrams

Collagen Type Chain Composition Gene Symbol(s) for Peptide Chains Localization/Function  
Type I The most abundant collagen type: found in bone, tendon, ligament, blood vessels, intervertebral disks  
  Two α1(I), one α2(I) COL1A1, COL1A2
  Product No. Sigma Type Suitability Testing Form Species Source
  C4387 V Substrate Powder Bovine achilles tendon
  C9879   Substrate Powder Bovine achilles tendon
  C3511 III   Powder Bovine calf skin
  C8919     Solution Bovine calf skin
  C9791   Cell Culture Powder Bovine calf skin
  C5983     Powder Human lung
  C7774 VII   Powder Human placenta
  C5483     Powder Human skin
  C1809 I Cell Culture Powder Kangaroo tail
  C8897 VII   Powder Rat tail
  C3929     Powder Kangaroo tail
  C7661   Cell Culture Powder Rat tail
  C5608     Powder Rabbit  
  C2124   Cell Culture  Solution Bovine hide 
  C2249   Cell Culture  Solution Human  
Type II Major protein component of cartilage  
  Three α1(II) COL2A1
  Product No. Sigma Type Suitability Testing Form Species Source
  C7806     Powder Bovine nasal septum
  C9301   Cell Culture Powder Chicken sternal cartilage
  C5733     Powder Murine sternum
  C1188     Powder Bovine tracheal cartilage
Type III The second most abundant collagen type: found colocalized with Type I in elastic tissues such as skin and blood vessels  
  Three α1(III) COL3A1
  Product No. Sigma Type Suitability Testing Form Species Source
  C4407 X   Powder Human placenta
Type IV Primary protein component of the basal lamina  
  Predominantly Two α1(IV) and one α2(IV), heterotrimers may be composed of six different α(IV)chains COL4A1, COL4A2, COL4A3, COL4A4, COL4A5, COL4A6
  Product No. Sigma Type Suitability Testing Form Species Source
  C7521 VI   Powder Human placenta
  C5533   Cell Culture Powder Human placenta
  C0543   Cell Culture Powder Murine basement membrane
Type V May be associated with collagen fibril organization and epithelial cell cycle inhibition  
  One α1(V), one α2(V), one α3(V) COL5A1, COL5A2, COL3A3
  Product No. Sigma Type Suitability Testing Form Species Source
  C3657 IX   Powder Human placenta
Type VI Found in most interstitial tissue, functions to anchor cells to the ECM framework, binds to the core protein component of decorin  
  One α1(VI), one α2(VI), one α3(VI) COL6A1, COL6A2, COL6A3
Type VII Anchoring fibrils of the subbasal lamina underlying epithelia  
  Three α1(VII) COL7A1
Type VIII A nonfibrillar short-chain collagen associated vascular endothelial cells and connective tissue  
  Three α1(VIII) COL8A1, COL8A2
Type IX Covalently cross-linked to Type II collage in cartilage  
  One α1(IX), one α2(IX), one α3(IX) COL9A1, COL9A2, COL9A3
Type X Associated with the hypertrophic chondrocytes growth plate during endochondral growth of long bones  
  Three α1(X) COL10A1
Type XI Closely related to Type V collagen  
  One α1(XI), one α2(XI), one α3(XI) COL11A1, COL11A2
Type XII Some sequence homology with Type IX. Present in tendons, ligaments, perichondrium, and periosteum, tissues containing Type I collagen  
  α1(XII) COL12A1

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