Studies on the low molecular weight proteins of human lens

The final peak from the gel filtration fractionation of human lens proteins has been called either low-molecular-weight protein or ψ-crystallin. Since this fraction has been shown to be heterogeneous we have attempted to determine which of its components are really γ-crystallin. At least four distinct components have been found with molecular weights determined as 24000, 21000, 19000 and 10000. The 19000 dalton species was isolated and shown to be ψ-crystallin on the basis of immunochemical reactivity, conformational analysis by ultraviolet circular dichroism and molecular size and charge. The 10000 dalton species increases with age in the human lens and probably is the product of degradation of lens cyrstallins. It does not show cross-reactivity with antiserum specific for γ-crystallin. The 24000 and 21000 dalton components have not been separated from each other. The mixture of these two components clearly contains material related to β-crystallin immunochemically, but reacts only very weakly, if at all, with anti α-crystallin serum.