Isoelectric focusing of embryonic cow lens crystallins

Abstract Soluble lens crystallins from several embryonic stages and also from adult cow lens cortex are compared by thin layer isoelectric focusing, immunoelectrophoresis, immuno-osmophoresis and antigen/antibody crossed electrophoresis. A gradual change in crystallin composition is found between the lens proteins of 1·5–7 month embryos. Thin layer isoelectric focusing studies of various embryonic stages from 1·5 to 7 months show a decrease of γ-crystallins along with an increase of β-crystallins and a slight increase of α-crystallins. When compared with the adult lens nucleus, the cortex shows a sharp decrease in concentration of γ-crystallin components. In addition, the composition of γ-crystallin of embryonic lens is similar to that of the adult lens nucleus, but different from that of the adult lens cortex. This difference appears due to certain components of γ-crystallin that are absent or present in lower amounts in the adult lens cortex compared with the embryonic lens. The same number of α-, β- and γ-crystallin antigens are present, they differ only in the relative concentration of the protein components. In all embryonic stages two pre-α-crystallins could be detected. These pre-α-crystallins have a high anodic mobility and appear to have a molecular weight lower than α-crystallin itself; the pre-α-crystallin is found to be eluted with the low molecular weight β-crystallins in Sepharose gel chromatography. By gel chromatography procedure, crystallins of cow lens cortex could be separated into five fractions; α 1 -crystallins of a molecular weight > 2,000,000, α 2 -crystallins, two β-crystallin fractions and γ-crystallin. Immuno-osmophoresis analysis shows that α 1 -crystallin is present in higher amounts in embryonic lens, and in adult lens nucleus it is higher than in adult lens cortex, while the α 2 -crystallin is present both in cortex and nucleus.