Gamma-crystallin A is a
protein that in humans is encoded by the CRYGAgene.[5]
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.[5]
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Shiloh Y, Donlon T, Bruns G, et al. (1986). "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.
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Salim A, Zaidi ZH (2003). "Homology models of human gamma-crystallins: structural study of the extensive charge network in gamma-crystallins". Biochem. Biophys. Res. Commun. 300 (3): 624–30.
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