Crystallin
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Overview
In biology, a crystallin is a water-soluble structural protein found in the lens of the eye, accounting for the transparency of the structure. It has also been identified in other places such as the heart [1] and aggressive breast cancer tumors [1]. Since it has been shown that lens injury may promote nerve regeneration[1], crystallin has been an area of neural research. So far, it has been demonstrated that crystallin ß b2 (crybb2) may be a neurite promoting factor [1].
Function
The main function of crystallins at least in the lens (anatomy) of the eye is probably to increase the refractive index while not obstructing light. However, this is not their only function. It is becoming increasingly clear that crystallins may have a several metabolic and regulatory functions, both within the lens and in other parts of the body [1].
Enzyme activity
Interestingly and perhaps excitingly from an evolutionary perspective, some crystallins are active enzymes.[1][1] A number of crystallins are related to the serine and tyrosine proteases, and others to quinone oxidoreductases. Whether these crystallins are products of a happy accident of evolution, in that these particular enzymes happened to be transparent, or whether the enzymatic activity is a part of the protective machinery of the lens, is an active research topic.[1]
Classification
Crystallins from a vertebrate eye lens are classified into three types: alpha, beta and gamma crystallins. These distinctions are based on the order in which they elute from a gel filtration chromatography column. These are also called ubiquitous crystallins. Beta- and gamma-crystallins are similar in sequence, structure and domains topology, and thus have been grouped together as a protein superfamily called βγ-Crystallins. The α-crystallin superfamily and βγ-crystallins compose the major superfamily of proteins present in the crystalline lens.
In addition to these crystallins there are other taxon-specific crystallins which are only found in the lens of some organisms; these include delta, epsilon, tau, and iota-crystallins. For example, alpha, beta, and delta crystallins are found in avian and reptilian lenses, and the alpha, beta, and gamma families are found in the lenses of all other vertebrates.
External links
- Graw J (1997). "The crystallins: genes, proteins and diseases". Biol Chem 378 (11): 1331-48. PMID 9426193.
- MeSH Crystallins
- Lens Crystallin Crystal Structures by Christine Slingsby, Birkbeck Colleg
References
Eye proteins | |
|---|---|
| Opsin (retinylidene protein) | Rhodopsin - Melanopsin - Photopsin |
| Crystallin | Alpha crystallin |
| Other | Arrestin - Guanylate cyclase activator - Recoverin - Rhodopsin kinase |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
