Alpha crystallin/Small heat shock protein, animal type
IPR001436
Definition
This entry represents a group of alpha-crystallin domain containing proteins from animals, including the A and B subunits (or chains) of alpha-crystallin and related small heat shock proteins. HSPs can be divided into HSP100, HSP90, HSP70, HSP60, HSP40 and small heat shock proteins (sHSPs) according to their molecular weight and homology. Small heat shock proteins contain an alpha-crystallin domain and variable N- and C-terminal extensions. sHsps are generally active as large oligomers consisting of multiple subunits, and are believed to be ATP-independent chaperones that prevent aggregation and are important in refolding in combination with other Hsps [[cite:PMID:10950306], [cite:PMID:11875128]]. The crystallins are water-soluble structural proteins that occur in high concentration in the cytoplasm of eye lens fibre cells. Four major groups of crystallin have been distinguished on the basis of size, charge and immunological properties: alpha-, beta-and gamma-crystallins occur in all vertebrate classes (though gamma-crystallins are low or absent in avian lenses); and delta-crystallin is found exclusively in reptiles and birds [[cite:PMID:2688200], [cite:PMID:7634077]]. Alpha-crystallin occurs as large aggregates, comprising two types of related subunits or chains (A and B) that are highly similar to the small (15-30kDa) heat shock proteins (HSPs), particularly in their C-terminal halves. The relationship between these families is one of classic gene duplication and divergence, from the small HSP family, allowing adaptation to novel functions. Divergence probably occurred prior to evolution of the eye lens, alpha-crystallin being found in small amounts in tissues outside the lens PMID:2688200. Alpha-crystallin has chaperone-like properties including the ability to prevent the precipitation of denatured proteins and to increase cellular tolerance to stress PMID:15575808. It has been suggested that these functions are important for the maintenance of lens transparency and the prevention of cataracts. This is supported by the observation that alpha-crystallin mutations show an association with cataract formation.
8 human proteins with this domain
Each is a reviewed human protein in the Seroatlas serome and a potential autoantibody target; this domain groups them into one antibody-relevant category. Every entry links to its own record.
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