Background of the antigen
Crystallins are the major proteins of the vertebrate eye lens, where they maintain the transparency and refractive index of the lens. Crystallins are divided into a, b, and g families, and the b- and g-crystallins also comprise a superfamily. Crystallins usually contain seven distinctive protein regions, including four homologous motifs, a connecting peptide, and N- and C-terminal extensions. b-crystallins constitute the major lens structural proteins. They associate into dimers, tetramers, and higher order aggregates. The b-crystallin subfamily is composed of several gene products, including bA1-, bA2-, bA3-, bA4-, bB1-, bB2- and bB3-crystallin. The bA1- and bA3-crystallin proteins are encoded by a single mRNA. They differ by only 17 amino acids, and bA1-crystallin is generated by use of an alternate translation initiation site. The genes for bA4-, bB1-, bB2- and bB3-crystallin are clustered on human chromosome 22q11, while the genes for bA3/A1- and bA2-crystallin map to human chromosomes 17q11 and 2q34, respectively.
