Lectins as probes of glycoprotein and glycolipid oligosaccharides in rods and cones.
The oligosaccharides of rod and cone membranes were investigated with the aid of fluorescence and (125)I-labeled lectins. Additionally, the ability of lectins to cause agglutination in ROS suspensions was used as an index for the presence of the corresponding lectin receptors. The specificities of lectin-ligand interactions were determined from studies of inhibition by various haptene sugars. The membranes of both rods and cones have receptors for Con A, PNA, RCA-120, RCA-60, SBA and WGA. The affinity of PNA for accessory cones is much higher than for the principal cones. There do not appear to be receptors for UeA and LTA on rods or cones. Additionally, receptors for HPA and DBA were identified on ROS. These results suggest the existance of the following sugar residues: There is no evidence for . The binding of Con A and WGA to ROS membrane proteins electrophoresed on SDS-polyacrylamide gels was also investigated. In addition to rhodopsin, these lectins also bind to the 291,000-dalton protein, indicating that it is a glycoprotein containing mannose and G1cNAc.
Bridges
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Cullen Eye Institute Baylor College of Medicine Department of Ophthalmology Houston, Texas 77030 USA.
Fong
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