Introduction

The crystallins are an important class of globular proteins whose functions are important in human vision. In particular, one member of this family, the γ-crystallins, has been extensively studied experimentally. The γ-crystallins, along with lysozyme and hemoglobin, are the most studied of the globular proteins. As is the case with lysozyme and hemoglobin, the γ-crystallins exhibit a metastable phase separation curve that has coexisting protein-poor and protein-rich phases. Indeed, when scaled with the appropriate variables, both lysozyme and γ-crystallin have very similar phase diagrams [16]. In this chapter we review what is known about the family of crystallins and their relationship to the formation of cataracts.

Understanding the molecular basis of vision is obviously of great importance. Long ago, nearsightedness was corrected using refractive lenses; today, newer scientific advances allow surgical procedures to eliminate nearsightedness. Other disorders and diseases, however, can impair our vision. Cataract disease is one example; it is often associated with aging and usually manifests itself sometime in late adulthood in certain individuals. Other forms of the disease occur in individuals at a much earlier age, even afflicting young adults and infants, often called juvenile cataracts. In both types of cataracts, blindness can occur if the disease is left untreated.