Canavalia ensiformis (Concanavalin A, Jackbean) (Jack bean)

Lectins are derived from the extracts of plants, animals, viruses and microorganisms. They are known to agglutinate red blood cells. These agglutinins can select cell types according to blood group activities utilizing sugar-binding mechanisms. Lectins form precipitates with glycoconjugates which is useful for identifying or separating oligosaccharides with identical sugar compositions such as galactose, mannose or glucose. Con A exists as a dimer below pH 5.0 and a tetramer in alkaline pH. Isolated from Canavalia ensiformis (Jack bean) seeds 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. 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. "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. Con A has an isoelectric point of about pH 5 and requires calcium or manganese ions at each of its four saccharide binding sites. Although these divalent metal ions are bound tightly to the polypeptide structure, buffers which can bind calcium (such as phosphate) generally should be avoided in diluting Con A, since a gradual loss in activity may occur. , Carbohydrate Specificity:, a-mannose, a-glucose, branched mannose, Inhibitory Carbohydrates: Methyl-a-D-mannopyranoside --> a-D-mannose --> a-D-glucose, Inhibiting/Eluting Sugar: 200mM a-methyl mannoside/200mM a-methyl glucoside mixture, Quality Control: SDS-PAGE, Reconstitution: Reconstitute in 10mM HEPES buffered saline, pH 8.5, 0.1mM Ca2+. 0.08% sodium azide can be used as preservative. For dissolving the lectin, add the lectin slowly to the buffer rather than adding the buffer to the lectin. Allow the lectin to dissolve without vigorous agitation. Storage and Stability: Lyophilized powder may be stored at -20°C. Stable for 12 months at -20°C. Reconstitute with 10mM HEPES buffered saline, pH 8.5, 0.1mM Ca2+. Aliquot and store at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.