They are classified as either: However, most recent studies suggest that the triple-helical regions have structures and properties specific for each type, particularly in their intermolecular interactions. Fibrillar collagens happen to be the most abundant, they offer the structural support and enabling cell motion. Pepsin-treated acid-soluble collagen from calf skin 0.
The structure, assembly , and supramolecular aggregation of type I collagen is the prototype from which has developed our understanding of collagenous structure, particularly the fibrillar collagens.
The existence of a family of collagenous proteins in the connective tissues of vertebrates was first id when cartilage collagen type II was found to be genetically distinct from the type I collagen of skin and tendon. As a result, skin can become fragile and less elastic.
One of the 10 or so subtypes of the disease called Ehlers-Danlos syndrome, which can lead to a fatal rupture of blood vessels, is caused by a mutation in the gene that codes for type III collagen. Spongin could be the closest descendent of a collagen that came out aroung enough time of milticelularity. The type I collagen helical molecule is a heterotrimer com two identical a1 I chains and one a2 I chain.
Figure 1. Cross linking is usually catalysed by the enzyme lysyl oxidase. On either side of the lamina densa are the lamina lucida and the lamina fibroreticularis. Search WWH:: An alternative approach for classifying the collagens depends on supramolecular structures that migh related to their physiological function.
Each tropocollagen is approximately 300 nm long and 1. The interrupted sites are speculated to lower the stabil the triple helix and might form kinks in the rod-like triple helix.
Thus, collagen helix that is otherwis unsusceptible to many proteinases might become susceptible at the interrupted sites of Gly—X—Y i. Known a chains.
In a disease called osteogenesis imperfecta, either type I collagen is not made in sufficient quantities or the collagen that is synthesized is defective in its composition. The content of lar hydrophobic residues in the collagenous triple helices also classifies the collagenous proteins into tw groups. Note that there is a groove on the surface of the helix.