Topological correlation between the cell‐recognition protein, R‐cognin and α‐bungarotoxin receptor in retinal plasma membrane

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Abstract
The amount of the neural retina cell recognition protein, R-cognin, in the plasma membrane of chick embryo neural retina cells declined 43% between 10 and 17 days of embryonic development. Over this period there was a 27% increase in the plasma membrane content of the α-bungarotoxin receptor. Plasma membranes of both these ages were sonicated into vesicles and these vesicles partitioned on α-bungarotoxin agarose beads into those which contained detectable α-bungarotoxin receptor and those which did not. At 10 days, approximately 6% of the plasma membrane vesicles contained receptor. At 17 days, <2% did. At 10 days, 60% of the R-cognin was found in the α-bungarotoxin receptor-containing vesicles, at 17 days 86%. At 17 days, 6% of the retina membrane with a high concentration of both α-bungarotoxin receptor and R-cognin was of a density indicative of it being of synaptic origin. These results suggested that R-cognin and α-bungarotoxin receptor occurred close together in the plasma membrane of retina cells. However, the lack of competition between R-cognin gamma globulin and specific α-bungarotoxin binding indicated that the α-bungarotoxin receptor and R-cognin were not the same protein. Thus, R-cognin and the α-bungarotoxin receptor appear to be separate proteins which occur in close proximity on the retina plasma membrane.