Analysis of a distinctive protein in chick retina during development

Soluble proteins from the chick retina were analyzed at various developmental stages by SDS-polyacrylamide gel electrophoresis. A peptide of about 24,000 daltons (24 Kd protein) appeared in the 14-day embryo and gradually increased with embryonic age, maintaining a fairly steady level after hatching. Polypeptides which correspond to actin and tubulin, however, remained almost unchanged during development. The 24 Kd protein was not detected in the cerebrum, tectum, pigment epithelium or vitreous body at any age. To characterize this protein, it was partially purified by gel filtration and ion exchange column chromatography, and its isoelectric point was measured. It was focused in a diffuse spot at about pH 5.5. In the bovine retina, a protein was observed at 24,000 daltons on SDS-polyacrylamide gel, but its isoelectric point was more basic than that of chick retina. It is suggested that the 24 Kd protein is one of the distinctive proteins that increase in concentration during the chick retinal development, and would be closely associated with retinal functions.