Protein--carbohydrate interaction. XVI. The interaction of concanavalin A with dextrans from L. mesenteroides B-512-F, L. mesenteroides 9birmingham), Streptococcus bovis, and a synthetic alpha-(1--6)-D-glucan

Carbohydrate binding properties of banana (Musa acuminata) lectin I. Novel recognition of internal alpha1,3-linked glucosyl residues

Examination of lectins of banana (Musa acuminata) and the closely related plantain (Musa spp.) by the techniques of quantitative precipitation, hapten inhibition of precipitation, and isothermal titration calorimetry showed that they are mannose/glucose binding proteins with a preference for the alpha-anomeric form of these sugars. Both generate precipitin curves with branched chain alpha-mannans (yeast mannans) and alpha-glucans (glycogens, dextrans, and starches), but not with linear alpha-glucans containing only alpha1,4- and alpha1,6-glucosidic bonds (isolichenan and pullulan). The novel observation was made that banana and plantain lectins recognize internal alpha1,3-linked glucosyl residues, which occur in the linear polysaccharides elsinan and nigeran. Concanavalin A and lectins from pea and lentil, also mannose/glucose binding lectins, did not precipitate with any of these linear alpha-glucans. This is, the authors believe, the first report of the recognition of internal alpha1,3-glucosidic bonds by a plant lectin. It is possible that these lectins are present in the pulp of their respective fruit, complexed with starch.

Immunochemical and related interactions with dextrans reviewed in terms of improved structural information

Structurally diverse dextrans from Leuconostoc mesenteroides and related bacteria have been used extensively in fundamental immunochemical studies such as induction and characterization of anti-dextran antibodies, as well as in studies of their interaction with pneumococcal antisera, normal bovine serum, concanavalin A, dextran-binding myeloma immunoglobulins and hybridoma antibodies. The inherent lack of specificity of structural data obtained by POSA and general lack of insight into other limitations of these analyses has often led to inaccurate and superficial interpretations. Proper interpretation of past and future studies necessitates pointing out previous inadequacies of dextran structural data and detailing more recently acquired structural information on the dextrans. Unambiguous terminology has been achieved by a new system of linkage symbols that includes the designation of structural positions, such as (1----3; l)- and (1----3; b) as linear-chain and branch-point positions, respectively. Results of immunological studies are reviewed. Improved interpretations and correlations are made on the basis of structural data from MSA and several other techniques which have become available on the dextrans.

Studies on the combining sites of concanavalin A

The initial event in the biological activity of concanavalin A (Con A) involves binding of the protein to cell surface receptors. The nature and mechanism whereby such binding may occur is described in terms of cell surface carbohydrates and the demonstrated specificity of the protein. Although considerable latitude is tolerated at the C-2 position of the alpha-D-hexopyranose ring system, the carbohydrate binding site of Con A appears to be complemnetary to alpha-D-mannopyranosyl residues. Hapten inhibition studies indicate that each of the hydroxyl groups of this sugar is probably involved in the binding mechanism. Of the common sugars present on cell surfaces (D-glucose, D-mannose and N-acetyl-D-glucosamine), it is probably alpha-D-mannopyranosyl residues which react with Con A. Since the latter units are primary receptors for Con A. Evidence supporting this view includes hapten inhibition studies with model oligosaccarides and preciptin studies with macromolecules containing internal 2-o-substituted alpha-D-mannopyranosyl residues. The binding to Con A of a series of oligosaccharides containing alpha-(1leads to2)-linked D-mannosyl units appears to increase up to the tetraose and then decreases; several possible explanations are considered. Acetylated Con A, although retaining its specificity, is about 50% as active as the native protein. Some biological properties of the modified protein are described. Data suggesting that Con A behaves differently in the solution phase than in the crystalline state are presented in terms of UV difference displacement studies. It is suggested that the so-called carbohydrate binding site reportedly identified in Con A crystals may not be correct.