Specificity of alpha crystallin binding to the lens membrane

The A1, A2, B1, and B2 species of bovine alpha crystallin have been purified and renatured to form high molecular weight aggregates comprised of only one species, and the aggregated forms of each of these species have been tested for their ability to bind to lens membrane in vitro. The aggregated forms of alpha-A1 and alpha-A2 bound to membrane in a saturable manner while those of alpha-B1 and alpha-B2 bound in much lower amounts, in a manner inconsistent with saturable binding. Together, these results demonstrate specific and saturable binding of aggregated alpha-A1 and alpha-A2 to the lens membrane, suggesting that these species are responsible for the previously observed interaction between alpha crystallin and the lens fiber cell membrane.