Distribution of cell surface saccharides on pancreatic cells

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Abstract
A simple, general procedure for the purification of a variety of lectins, and for the preparation of lectin-ferritin conjugates of defined molar composition and binding properties used as probes for cell surface saccharides was described. The technique uses a universal affinity column for lectins and their conjugates, which consists of hog sulfated gastric mucin glycopeptides covalently coupled to agarose. The procedure involves the following: purification of lectins by chromatography of aqueous extracts of seeds or other lectin-containing fluids over the affinity column, followed by desorption of the desired lectin with its hapten sugar; iodination of the lectin to serve as a marker during subsequent steps; conjugation of lectin to ferritin with glutaraldehyde; collection of active lectin-ferritin conjugates by affinity chromatography; and separation of monomeric lectin-ferritin conjugates from larger aggregates and unconjugated lectin by gel chromatography. Based on radioactivity and absorbancy at 310 nm for lectin and ferritin, respectively, the conjugates consist of 1-2 molecules of lectin per ferritin molecule. Binding studies of native lectins and their ferritin conjugates to dispersed [guinea pig, rat] pancreatic acinar cells showed that the conjugation procedure does not significantly alter the affinity constant of the lectin for its receptor on the cell surface or the number of sites detected.