Structural requirements of carbohydrates to bind Agaricus bisporus lectin |
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Authors: | Irazoqui FJ; Vides MA; Nores GA |
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Institution: | Departamento de Bioquimica Clinica and Departamento de Quimica Biologica-CIQUIBIC-CONICET, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Agencia Postal 4, CC 61, 5000 Cordoba, Argentina. |
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Abstract: | Galbeta1-3GalNAc (T-disaccharide) and related molecules were assayed to
describe the structural requirements of carbohydrates to bind Agaricus
bisporus lectin (ABL). Results provide insight into the most relevant
regions of T-disaccharide involved in the binding of ABL. It was found that
monosaccharides bind ABL weakly indicating a more extended
carbohydrate-binding site as compared to those involvedin the T-
disaccharide specific lectins such as jacalin and peanut agglutinin.
Lacto-N-biose (Galbeta1-3GlcNAc) unlike T-disaccharide, is unable to
inhibit the ABL interaction, thus showing the great importance of the
position of the axial C-4 hydroxyl group of GalNAc in T-disaccharide. This
finding could explain the inhibitory ability of Galbeta1-6GlcNAc and
lactose because C-4 and C-3 hydroxyl groups of reducing Glc, respectively,
occupy a similar position as reported by conformational analysis. From the
comparison of different glycolipids bearing terminal T-disaccharide bound
to different linkages, it can be seen than ABL binding is even more
impaired by an adjacent C-6 residual position than by the anomeric
influence of T-disaccharide. Furthermore, the addition of beta-GlcNAc to
the terminal T-disaccharide in C-3 position of Gal does not affect the ABL
binding whereas if an anionic group such as glucuronic acid is added to
C-3, the binding is partially affected. These findings demonstrate that ABL
holds a particular binding nature different from that of other
T-disaccharide specific lectins.
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