Crystallin
| Alpha crystallin A chain, N terminal | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Crystallin | ||||||||
| Pfam | PF00525 | ||||||||
| InterPro | IPR003090 | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
| Beta/Gamma crystallin | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Crystall | ||||||||
| Pfam | PF00030 | ||||||||
| InterPro | IPR001064 | ||||||||
| PROSITE | PDOC00197 | ||||||||
| SCOP | 4gcr | ||||||||
| SUPERFAMILY | 4gcr | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
In anatomy, a crystallin is a water-soluble structural protein found in the lens and the cornea of the eye accounting for the transparency of the structure. It has also been identified in other places such as the heart, and in aggressive breast cancer tumors. Since it has been shown that lens injury may promote nerve regeneration, crystallin has been an area of neural research. So far, it has been demonstrated that crystallin β b2 (crybb2) may be a neurite-promoting factor.
The main function of crystallins at least in the lens of the eye is probably to increase the refractive index while not obstructing light. However, this is not their only function. It has become crystal clear that crystallins may have several metabolic and regulatory functions, both within the lens and in other parts of the body. More proteins containing βγ-crystallin domains have now been characterized as calcium binding proteins with Greek key motif as a novel calcium-binding motif.
Interestingly and perhaps excitingly from an evolutionary perspective, some crystallins are active enzymes, while others lack activity but show homology to other enzymes. The crystallins of different groups of organisms are related to a large number of different proteins, with those from birds and reptiles related to lactate dehydrogenase and argininosuccinate lyase, those of mammals to alcohol dehydrogenase and quinone reductase, and those of cephalopods to glutathione S-transferase and aldehyde dehydrogenase. Whether these crystallins are products of a fortuitous accident of evolution, in that these particular enzymes happened to be transparent and highly soluble, or whether these diverse enzymatic activities are part of the protective machinery of the lens, is an active research topic. The recruitment of protein that originally evolved with one function to serve a second, unrelated function is an example of an exaptation.
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Wikipedia