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 alpha, beta, and gamma families, and the beta and gamma-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. gamma-crystallins are structural proteins in the lens, and they exists as monomers which typically lack connecting peptides and terminal extensions. The gamma-crystallins include seven closely related gamma A, gamma B, gamma C, gamma D, gamma E, gamma F, and gamma G-crystallin, as well as the gamma N and gamma S-crystallin genes. The gamma-crystallins are differentially regulated after early development, and are involved in cataract formation as a result of either age-related protein degradation or genetic mutation.
