Crystallin, Alpha B (CRYAB) Recombinant Protein

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. Elevated expression of alpha-B crystallin occurs in many neurological diseases; a missense mutation cosegregated in a family with a desmin-related myopathy. [provided by RefSeq, Jul 2008]

CRYAB: a major structural protein of the eye lens. A member of the small heat shock protein (sHSP also known as the HSP20) family. Alpha-B is expressed in the lens as well as other tissues. Elevated expression of alpha-B crystallin occurs in many neurological diseases; a missense mutation cosegregated in a family with a desmin-related myopathy.

Protein type: Chaperone; Heat shock protein

Chromosomal Location of Human Ortholog: 11q22.3-q23.1

Cellular Component: microtubule cytoskeleton; Golgi apparatus; cell surface; mitochondrion; cytoplasm; actin filament bundle; plasma membrane; Z disc; cytosol; nucleus

Molecular Function: identical protein binding; protein binding; protein homodimerization activity; metal ion binding; microtubule binding; unfolded protein binding; structural constituent of eye lens

Biological Process: lens development in camera-type eye; muscle development; protein folding; microtubule polymerization or depolymerization; stress-activated MAPK cascade; negative regulation of caspase activity; response to estradiol stimulus; tubulin folding; muscle contraction; response to hydrogen peroxide; negative regulation of intracellular transport; response to hypoxia; negative regulation of cell growth; protein homooligomerization; aging; negative regulation of apoptosis

Disease: Cataract 16, Multiple Types; Myopathy, Myofibrillar, Fatal Infantile Hypertonic, Alpha-b Crystallin-related; Myopathy, Myofibrillar, 2; Cardiomyopathy, Dilated, 1ii