Crystallins are separated into two classes: taxon-specific, or enzyme, and ubiquitous. The latter class constitutes the major proteins of vertebrate eye lens and maintains the transparency and refractive index of the lens. Since lens central fiber cells lose their nuclei during development, these crystallins are made and then retained throughout life, making them extremely stable proteins. Mammalian lens crystallins are divided into alpha, beta, and gamma families; beta and gamma crystallins are also considered as a superfamily. Alpha and beta families are further divided into acidic and basic groups. Seven protein regions exist in crystallins: four homologous motifs, a connecting peptide, and N- and C-terminal extensions. Alpha crystallins are composed of two gene products: alpha-A and alpha-B, for acidic and basic, respectively. Alpha crystallins can be induced by heat shock and are members of the small heat shock protein (sHSP also known as the HSP20) family. They act as molecular chaperones although they do not renature proteins and release them in the fashion of a true chaperone; instead they hold them in large soluble aggregates. Post-translational modifications decrease the ability to chaperone. These heterogeneous aggregates consist of 30-40 subunits; the alpha-A and alpha-B subunits have a 3:1 ratio, respectively. Two additional functions of alpha crystallins are an autokinase activity and participation in the intracellular architecture. Alpha-A and alpha-B gene products are differentially expressed; alpha-A is preferentially restricted to the lens and alpha-B is expressed widely in many tissues and organs. Defects in this gene cause autosomal dominant congenital cataract (ADCC).^[5]

Interactions[edit]

CRYAA has been shown to interact with CRYBB2,^[6] Hsp27,^[6] CRYGC^[6] and CRYAB.^[6]

References[edit]

^ ^a ^b ^c GRCh38: Ensembl release 89: ENSG00000160202 – Ensembl, May 2017

^ ^a ^b ^c GRCm38: Ensembl release 89: ENSMUSG00000024041 – Ensembl, May 2017

^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.

^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.

^ ^a ^b "Entrez Gene: CRYAA crystallin, alpha A".

^ ^a ^b ^c ^d Fu, Ling; Liang Jack J-N (Feb 2002). "Detection of protein-protein interactions among lens crystallins in a mammalian two-hybrid system assay". J. Biol. Chem. 277 (6). United States: 4255–60. doi:10.1074/jbc.M110027200. ISSN 0021-9258. PMID 11700327.

External links[edit]

Human CRYAA genome location and CRYAA gene details page in the UCSC Genome Browser.

Further reading[edit]

Derham BK, Harding JJ (1999). "Alpha-crystallin as a molecular chaperone". Progress in Retinal and Eye Research. 18 (4): 463–509. doi:10.1016/S1350-9462(98)00030-5. PMID 10217480. S2CID 25124893.

de Jong WW, Terwindt EC, Bloemendal H (1976). "The amino acid sequence of the A chain of human alpha-crystallin". FEBS Lett. 58 (1): 310–3. doi:10.1016/0014-5793(75)80286-9. PMID 817940. S2CID 83739751.

Ortwerth BJ, Slight SH, Prabhakaram M, et al. (1992). "Site-specific glycation of lens crystallins by ascorbic acid". Biochim. Biophys. Acta. 1117 (2): 207–15. doi:10.1016/0304-4165(92)90081-5. PMID 1525182.

Roquemore EP, Dell A, Morris HR, et al. (1992). "Vertebrate lens alpha-crystallins are modified by O-linked N-acetylglucosamine". J. Biol. Chem. 267 (1): 555–63. doi:10.1016/S0021-9258(18)48530-4. PMID 1730617.

Jaworski CJ, Piatigorsky J (1989). "A pseudo-exon in the functional human alpha A-crystallin gene". Nature. 337 (6209): 752–4. Bibcode:1989Natur.337..752J. doi:10.1038/337752a0. PMID 2918909. S2CID 4272504.

Hawkins JW, Van Keuren ML, Piatigorsky J, et al. (1987). "Confirmation of assignment of the human alpha 1-crystallin gene (CRYA1) to chromosome 21 with regional localization to q22.3". Hum. Genet. 76 (4): 375–80. doi:10.1007/BF00272448. PMID 3610158. S2CID 19506423.

McDevitt DS, Hawkins JW, Jaworski CJ, Piatigorsky J (1986). "Isolation and partial characterization of the human alpha A-crystallin gene". Exp. Eye Res. 43 (2): 285–91. doi:10.1016/S0014-4835(86)80098-7. PMID 3758227.

Caspers GJ, Pennings J, De Jong WW (1995). "A partial cDNA sequence corrects the human alpha A-crystallin primary structure". Exp. Eye Res. 59 (1): 125–6. doi:10.1006/exer.1994.1089. PMID 7835394.

Miesbauer LR, Zhou X, Yang Z, et al. (1994). "Post-translational modifications of water-soluble human lens crystallins from young adults". J. Biol. Chem. 269 (17): 12494–502. doi:10.1016/S0021-9258(18)99902-3. PMID 8175657.

Jaworski CJ (1996). "A reassessment of mammalian alpha A-crystallin sequences using DNA sequencing: implications for anthropoid affinities of tarsier". J. Mol. Evol. 41 (6): 901–8. Bibcode:1995JMolE..41..901J. doi:10.1007/bf00173170. PMID 8587135. S2CID 22878315.

Takemoto LJ (1996). "Differential phosphorylation of alpha-A crystallin in human lens of different age". Exp. Eye Res. 62 (5): 499–504. doi:10.1006/exer.1996.0060. PMID 8759518.

Prabhakaram M, Katz ML, Ortwerth BJ (1997). "Glycation mediated crosslinking between alpha-crystallin and MP26 in intact lens membranes". Mech. Ageing Dev. 91 (1): 65–78. doi:10.1016/0047-6374(96)01781-2. PMID 8910261. S2CID 53227438.

Andley UP, Mathur S, Griest TA, Petrash JM (1997). "Cloning, expression, and chaperone-like activity of human alphaA-crystallin". J. Biol. Chem. 271 (50): 31973–80. doi:10.1074/jbc.271.50.31973. PMID 8943244.

Lampi KJ, Ma Z, Shih M, et al. (1997). "Sequence analysis of betaA3, betaB3, and betaA4 crystallins completes the identification of the major proteins in young human lens". J. Biol. Chem. 272 (4): 2268–75. doi:10.1074/jbc.272.4.2268. PMID 8999933.

Lindner RA, Kapur A, Carver JA (1997). "The interaction of the molecular chaperone, alpha-crystallin, with molten globule states of bovine alpha-lactalbumin". J. Biol. Chem. 272 (44): 27722–9. doi:10.1074/jbc.272.44.27722. PMID 9346914.

Litt M, Kramer P, LaMorticella DM, et al. (1998). "Autosomal dominant congenital cataract associated with a missense mutation in the human alpha crystallin gene CRYAA". Hum. Mol. Genet. 7 (3): 471–4. doi:10.1093/hmg/7.3.471. PMID 9467006.

Takemoto LJ (1998). "Quantitation of asparagine-101 deamidation from alpha-A crystallin during aging of the human lens". Curr. Eye Res. 17 (3): 247–50. doi:10.1076/ceyr.17.3.247.5218. PMID 9543632.

Doss EW, Ward KA, Koretz JF (1998). "Investigation of the 'fines' hypothesis of primary open-angle glaucoma: the possible role of alpha-crystallin". Ophthalmic Res. 30 (3): 142–56. doi:10.1159/000055468. PMID 9618718. S2CID 46813838.