Table 1.
Primary types of collagens*
| Classes | Type | Genes encoding proteins typical of collagen composition | Description |
|---|---|---|---|
| Fibrillar | I | COL1A1 and COL1A2 | Quarter-stagger packed fibrils that are primarily found in fibrous stromal matrices, such as skin, bone, tendons and ligaments |
| II | COL2A1 | ||
| III | COL3A1 | ||
| V | COL5A1, COL5A2 and COL5A3 | ||
| XI | COL11A1, COL11A2 and COL11A3 | ||
| XXIV | COL24A1 | ||
| XXVII | COL27A1 | ||
| FACIT | IX | COL9A1, COL9A2 and COL9A3 | Fibril-associated molecular bridges that are associated with type I (XII, XVI, XIX, XXI) and type II (IX, XVI, XIX) collagen fibrils |
| XII | COL12A1 | ||
| XIV | COL14A1 | ||
| XVI | COL16A1 | ||
| XIX | COL19A1 | ||
| XX | COL20A1 | ||
| XXI | COL21A1 | ||
| XXII | COL22A1 | ||
| Basement membrane | IV | COL4A1, COL4A2, COL4A3, COL4A4, COL4A5 and COL4A6 | Network structure comprised of laminins and basement membrane proteins |
| Long chain | VII | COL7A13 | Anchoring fibrils that are associated with the basement membrane |
| Filamentous | VI | COL6A1, COL6A2, COL6A3, COL6A5 and COL6A6 | Beaded microfibrils |
| Short chain | VIII | COL8A1 | Hexagonal lattice structure |
| X | COL10A1 | These collagens both regulate, and are regulated by, hypertrophy in cartilage | |
| Multiplexins | XV | COL15A1 | Multiple triple helix domains with interruptions containing chondroitin sulphate and heparin sulphate glycosaminoglycans |
| XVIII | COL18A1 | ||
| MACIT (transmembrane domain) | XIII | COL13A1 | Cell surface molecules with extracellular, membrane-spanning and intracellular domains |
| XVII | COL17A1 | ||
| XXIII | COL23A1 |
*
Collagen types are classified on the basis of domain structure homology and suprastructural assembly.
FACIT, fibril-associated collagens with interrupted triple helices; MACIT, membrane-associated collagens with interrupted triple helices.