CRYGB explained

Gamma-crystallin B is a protein that in humans is encoded by the CRYGB gene.^[1]

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.

Gamma-crystallins are a homogeneous group of highly symmetrical, monomeric proteins typically lacking connecting peptides and terminal extensions. They are differentially regulated after early development. Four gamma-crystallin genes (gamma-A through gamma-D) and three pseudogenes (gamma-E, gamma-F, gamma-G) are tandemly organized in a genomic segment as a gene cluster. Whether due to aging or mutations in specific genes, gamma-crystallins have been involved in cataract formation.

Further reading

• Graw J . The crystallins: genes, proteins and diseases . Biol. Chem. . 378 . 11 . 1331–48 . 1998 . 9426193 . 10.1515/bchm.1997.378.11.1299 .
• Slingsby C, Clout NJ . Structure of the crystallins . Eye . 13 (Pt 3b) . 3. 395–402 . 2000 . 10627816 . 10.1038/eye.1999.113. free .
• Hearne CM, Todd JA . Trinucleotide repeat polymorphism at the CRYG1 locus . Nucleic Acids Res. . 19 . 19 . 5450 . 1991 . 1923840 . 10.1093/nar/19.19.5450-a . 328932 .
• Brakenhoff RH . Human gamma-crystallin genes. A gene family on its way to extinction . J. Mol. Biol. . 216 . 3 . 519–32 . 1991 . 2258929 . 10.1016/0022-2836(90)90380-5 . vanc. Aarts HJ . Reek FH . 3 . Lubsen . NH . Schoenmakers . JG .
• den Dunnen JT . Nucleotide sequence of the rat gamma-crystallin gene region and comparison with an orthologous human region . Gene . 78 . 2 . 201–13 . 1989 . 2777080 . 10.1016/0378-1119(89)90223-0 . vanc. van Neck JW . Cremers FP . 3 . Lubsen . N . Schoenmakers . J .
• Shiloh Y . Assignment of the human gamma-crystallin gene cluster (CRYG) to the long arm of chromosome 2, region q33-36 . Hum. Genet. . 73 . 1 . 17–9 . 1986 . 3011643 . 10.1007/BF00292656 . vanc. Donlon T . Bruns G . 3 . Breitman . M. L. . Tsui . Lap-Chee . 27997711 .
• Meakin SO, Du RP, Tsui LC, Breitman ML . Gamma-crystallins of the human eye lens: expression analysis of five members of the gene family . Mol. Cell. Biol. . 7 . 8 . 2671–9 . 1987 . 3670288 . 10.1128/mcb.7.8.2671. 367883 .
• den Dunnen JT, Moormann RJ, Cremers FP, Schoenmakers JG . Two human gamma-crystallin genes are linked and riddled with Alu-repeats . Gene . 38 . 1–3 . 197–204 . 1986 . 4065573 . 10.1016/0378-1119(85)90218-5 .
• Bonaldo MF, Lennon G, Soares MB . Normalization and subtraction: two approaches to facilitate gene discovery . Genome Res. . 6 . 9 . 791–806 . 1997 . 8889548 . 10.1101/gr.6.9.791 . free .
• Héon E . The gamma-crystallins and human cataracts: a puzzle made clearer . Am. J. Hum. Genet. . 65 . 5 . 1261–7 . 1999 . 10521291 . 10.1086/302619 . 1288278 . vanc. Priston M . Schorderet DF . 3 . Billingsley . Gail D. . Girard . Philippe Othenin . Lubsen . Nicolette . Munier . Francis L. .
• Santhiya ST . Novel mutations in the gamma-crystallin genes cause autosomal dominant congenital cataracts . J. Med. Genet. . 39 . 5 . 352–8 . 2002 . 12011157 . 10.1136/jmg.39.5.352 . 1735119 . vanc. Shyam Manohar M . Rawlley D . 3 . Vijayalakshmi . P . Namperumalsamy . P . Gopinath . PM . Löster . J . Graw . J .
• MacCoss MJ . Shotgun identification of protein modifications from protein complexes and lens tissue . Proc. Natl. Acad. Sci. U.S.A. . 99 . 12 . 7900–5 . 2002 . 12060738 . 10.1073/pnas.122231399 . 122992 . vanc. McDonald WH . Saraf A . 3 . Sadygov . R . Clark . JM . Tasto . JJ . Gould . KL . Wolters . D . Washburn . M . 2002PNAS...99.7900M . free .
• Strausberg RL . Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences . Proc. Natl. Acad. Sci. U.S.A. . 99 . 26 . 16899–903 . 2003 . 12477932 . 10.1073/pnas.242603899 . 139241 . vanc. Feingold EA . Grouse LH . 3 . Derge . JG . Klausner . RD . Collins . FS . Wagner . L . Shenmen . CM . Schuler . GD . 2002PNAS...9916899M . free .
• Salim A, Zaidi ZH . Homology models of human gamma-crystallins: structural study of the extensive charge network in gamma-crystallins . Biochem. Biophys. Res. Commun. . 300 . 3 . 624–30 . 2003 . 12507494 . 10.1016/S0006-291X(02)02895-4 .
• Nandrot E . Gamma-D crystallin gene (CRYGD) mutation causes autosomal dominant congenital cerulean cataracts . J. Med. Genet. . 40 . 4 . 262–7 . 2003 . 12676897 . 10.1136/jmg.40.4.262 . 1735438 . vanc. Slingsby C . Basak A . 3 . Cherif-Chefchaouni . M . Benazzouz . B . Hajaji . Y . Boutayeb . S . Gribouval . O . Arbogast . L .
• Lapko VN, Smith DL, Smith JB . Methylation and carbamylation of human gamma-crystallins . Protein Sci. . 12 . 8 . 1762–74 . 2004 . 12876325 . 10.1110/ps.0305403 . 2323962 .
• Salim A, Bano A, Zaidi ZH . Prediction of possible sites for posttranslational modifications in human gamma crystallins: effect of glycation on the structure of human gamma-B-crystallin as analyzed by molecular modeling . Proteins . 53 . 2 . 162–73 . 2004 . 14517968 . 10.1002/prot.10493 . 25233913 .
• Gerhard DS . The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC) . Genome Res. . 14 . 10B . 2121–7 . 2004 . 15489334 . 10.1101/gr.2596504 . 528928 . vanc. Wagner L . Feingold EA . 3 . Shenmen . CM . Grouse . LH . Schuler . G . Klein . SL . Old . S . Rasooly . R .

Notes and References

1. Web site: Entrez Gene: CRYGB crystallin, gamma B.