Crystallin

Beta- and gamma-crystallins (such as CRYGC) are similar in sequence, structure and domains topology, and thus have been grouped together as a protein superfamily called βγ-Crystallins.

They 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.

Alpha-crystallin occurs as large aggregates, comprising two types of related subunits (A and B) that are highly similar to the small (15-30kDa) heat shock proteins (sHsps), particularly in their C-terminal halves.

[13] Alpha-crystallin has chaperone-like properties including the ability to prevent the precipitation of denatured proteins and to increase cellular tolerance to stress.

The N-terminal domain of alpha-crystallin is not necessary for dimerisation or chaperone activity, but appears to be required for the formation of higher order aggregates.

Each motif, which is about forty amino acid residues long, is folded in a distinctive Greek key pattern.