Lens proteins consist almost entirely of crystallins (about 95%). Crystallins are also found vertebrate skeletal muscle tissue. In the lens, their structural function is to assist in maintaining the proper refractive index of the lens. The mammalian lens contains 3 major classes of crystallins: alpha, beta, and gamma. Alpha-crystallin is the largest of the crystallins and is composed of 2 primary gene products--alpha-A and alpha-B. There are at least 5 different proteins comprising the beta-crystallins. The gamma-crystallins are monomeric, but there are at least 5 gamma crystallins identified in bovine and rat lens. Alpha-Crystallin comprises 40% of total lens protein composition. In addition to maintaining proper refractive index, it also functions in a chaperone like manner by preventing the formation of aggregates possibly leading to cataract formation. It is believed that the phosphorylated states of the alpha-crystallin occur in response to cellular stress and may serve a structural control function and play a role in protein maintenance. Alpha-B crystallin has been linked to Alexander's disease where it accumulates in brain cells of those afflicted.
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Protein Aliases: AACRYA; alpha B-crystallin; Alpha crystallin B chain; Alpha(B)-crystallin; Alpha-crystallin B chain; CRYA2; CRYAB; crystallin, alpha 2; crystallin, alpha B; crystallin, alpha polypeptide 2; CTPP2; epididymis secretory protein Li 101; Heat shock protein beta-5; heat shock protein CryAB; heat shock protein HspB5; heat-shock 20 kD like-protein; HSPB5; NY REN 27 antigen; P23; Renal carcinoma antigen NY-REN-27; Rosenthal fiber component
Gene Aliases: AACRYA; BOS_14343; CMD1II; Crya-2; CRYA2; CRYAB; CTPP2; CTRCT16; HEL-S-101; HSPB5; MFM2; P23
Molecular Function: chaperone