Isothermal Titration Calorimetric Studies on the Binding of Deoxytrimannoside Derivatives with Artocarpin: Implications for a Deep-Seated Combining Site in Lectins
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- 作者：P. Geetha Rani ; Kiran Bachhawat ; G. Bhanuprakash Reddy ; Stefan Oscarson ; and Avadhesha Surolia
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：September 5, 2000
- 年：2000
- 卷：39
- 期：35
- 页码：10755 - 10760
- 全文大小：72K
- 年卷期：v.39,no.35(September 5, 2000)
- ISSN：1520-4995
文摘
The carbohydrate binding specificity of the seed lectin from Artocarpus integrifolia, artocarpin,has been elucidated by the enzyme-linked lectin absorbent assay [Misquith, S., et al (1994) J. Biol. Chem.269, 30393-30401], wherein it was demonstrated to be a Man/Glc specific lectin with high affinity forthe trisaccharide present in the core of all N-linked oligosaccharide chains of glycoproteins. As aconsequence of this characterization, the binding epitopes of this trisaccharide, 3,6-di(
-D-mannopyranosyl)-D-mannose, for artocarpin were investigated by isothermal titration calorimetry using its monodeoxy aswell as Glc and Gal analogues. The thermodynamic data presented here implicate 2-, 3-, 4-, and 6-hydroxylgroups of the (1-3) Man and (1-6) Man residues, and the 2- and 4-OH groups of the central Manresidue, in binding to artocarpin. Nevertheless, (1-3) Man is the primary contributor to the bindingaffinity, unlike other Man/Glc binding lectins which exhibit a preference for (1-6) Man. In addition,unlike the binding reactions of most lectins reported so far, the interaction of mannotriose involves all ofits hydroxyl groups with the combining site of the lectin. Moreover, the free energy and enthalpycontributions to binding of individual hydroxyl groups of the trimannoside estimated from the correspondingmonodeoxy analogues show nonlinearity, suggesting differential contributions of the solvent and proteinto the thermodynamics of binding of the analogues. Thus, this study not only provides evidence for theextended site recognition of artocarpin for the trimannoside epitope but also suggests that its combiningsite is best described as a deep cleft as opposed to shallow indentations implicated in other lectins.
-D-mannopyranosyl)-D-mannose, for artocarpin were investigated by isothermal titration calorimetry using its monodeoxy aswell as Glc and Gal analogues. The thermodynamic data presented here implicate 2-, 3-, 4-, and 6-hydroxylgroups of the (1-3) Man and (1-6) Man residues, and the 2- and 4-OH groups of the central Manresidue, in binding to artocarpin. Nevertheless, (1-3) Man is the primary contributor to the bindingaffinity, unlike other Man/Glc binding lectins which exhibit a preference for (1-6) Man. In addition,unlike the binding reactions of most lectins reported so far, the interaction of mannotriose involves all ofits hydroxyl groups with the combining site of the lectin. Moreover, the free energy and enthalpycontributions to binding of individual hydroxyl groups of the trimannoside estimated from the correspondingmonodeoxy analogues show nonlinearity, suggesting differential contributions of the solvent and proteinto the thermodynamics of binding of the analogues. Thus, this study not only provides evidence for theextended site recognition of artocarpin for the trimannoside epitope but also suggests that its combiningsite is best described as a deep cleft as opposed to shallow indentations implicated in other lectins.