SOLUBLE AND MEMBRANE LECTIN‐BINDING GLYCOPROTEINS OF THE CHROMAFFIN GRANULE

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Abstract
Abstract— Fluorescein isothiocyanate‐labelled lectins were used to identify lectin‐binding glycoproteins of the chromaffin granule after electrophoresis of the membrane and soluble granule proteins on sodium dodecyl sulphate polyacrylamide slab gels. The glycoprotein nature of all lectin‐binding bands was confirmed by staining the gels for carbohydrates, and the specificity of the lectin‐binding was demonstrated by hapten sugar inhibition of binding. In samples of granule membrane proteins reduced with dithiothreitol 10 concanavalin A (Con A), 5 wheat germ agglutinin, 8 Ricinus communis agglutinin‐60, and 7 Ricinus communis agglutinin‐120 (RCA‐120) binding glycoproteins were identified. Molecular weights of these glycoproteins varied from 20,000 to 200,000 daltons. All but two of the Con A‐binding bands and one of the RCA‐120 binding bands appeared to react with more than one lectin, suggesting possible carbohydrate heterogeneity in these membrane glycoproteins. The band identified as dopamine β‐hydroxylase reacted most intensely with all four lectin tested, and in the soluble core material this enzyme was the sole significant lectin binding glycoprotein.