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Con A is one of the most widely used and well characterized lectins. Con A has broad applicability primarily because it recognizes a commonly occurring sugar structure, a-linked mannose. Since a wide variety of serum and membrane glycoproteins have a “core oligosaccharide” structure which includes a-linked mannose residues, many glycoproteins can be examined or purified with Con A and its conjugates. Briefly, Con A has been utilized in hormone receptor studies, mitogenic assays, characterization of normal and malignant cells, glycoprotein purification, viral antigen isolation, dextran and mannan fractionation, cell agglutination studies, bacterial aggregation, membrane fluidity and lateral mobility investigations, turbidimetric assays for sugars, lymphokine production, as well as in many other applications.
At neutral and alkaline pH, Con A exists as a tetramer of four identical subunits of approximately 26,000 daltons each. Below pH 5.6, Con A dissociates into active dimers of 52,000 daltons. Acetylation, succinylation or other derivatizations can also produce stable forms with dimeric structures. (See succinylated Con A). “Native” Con A is a mixture of several forms of the lectin due to “nicks” occurring in the polypeptide chains. Although having little or no effect on the saccharide binding activity, these “nicks” in the sequence are often revealed even in the purest lectin preparations as additional bands in SDS-polyacrylamide gel electrophoresis. These hydrolytic cleavage sites appear to exist in the lectin as it occurs in the seeds and are not a function of isolation procedures. |