Analysis of Saccharide Binding to Artocarpus integrifolia Lectin Reveals Specific Recognition of T-antigen (\beta D-Gal(1\rightarrow 3)GalNAc

Sastry, MV and Banarjee, Probal and Patanjali, Sankhavaram R and Swamy, Joginadha M and Swarnalatha, GV and Surolia, Avadhesha (1986) Analysis of Saccharide Binding to Artocarpus integrifolia Lectin Reveals Specific Recognition of T-antigen (\beta D-Gal(1\rightarrow 3)GalNAc. In: Journal of Biological Chemistry, 261 (25). pp. 11726-11733.

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Abstract

The binding of Artocarpus integrifolia lectin to N-dansylgalactosamine (where dansyl is 5-dimethylaminonaphthalene-1-sulfonyl) leads to a 100\% increase in dansyl fluorescence with a concomitant blue shift in the emission maximum by 10 nm. This binding is carbohydrate-specific and has an association constant of 1.74 \times $10^4 M^{-1}$ at $20^oC$. The lectin has two binding sites for N-dansylgalactosamine. The values of -\Delta H and -\Delta S for the bindinogf N-dansylgalactosamine are in the range of values reported for severa lectin monosaccharide interactions, indicating an absence of non-polar interaction of the dansylmoiety of the sugar with the combining region of the protein. Dissociation of the bound N-dansylgalactosamine from its complex with the lectin and cosequent change in its fluorescence on addition of nonfluorescent sugars allowed evaluation of the association constant for competing ligands. The thermodynamic parameters for the binding of monosaccharides suggest that the OH groups at C-2, C-3, C-4, and C-6 in the D-galactose configuration are important loci for interaction with the lectin. The acetamido group at C-2 of 2-acetamido-2-deoxygalactopyranose and a methoxyl group at C-1 of methyl-\gamma -Dgalactopyranoside are presumably also involved in binding through nonpolar and van der Waals' interactions. The T-antigenic disaccharide Gal\beta 1\rightarrow 3GalNAc binds very strongly to the lectinw hen compared with methyl-\beta -D-galactopyranoside, the \beta ( 1\rightarrow 3)-linked disaccharides such as Gal\beta 1\rightarrow 3GalNAc, and the \beta (1\rightarrow 4)- linked disaccharides, N-acetyllactosamine andla ctose. The major stabilizing force for the avid binding of Tantigenic disaccharide appears to be a favorable enthalpic contribution. The combining site of the lectin is, therefore, extended. These data takent ogether suggest that the Artocarpus lectin is specific toward the Thomsen-Friedenreich (T) antigen. There are subtle differences in the overaltlo pography of its combining site when compared with that of peanut (Arachis hypogaea)agglutinin.The results of stopped flow spectrometry for the binding of N-dansylgalactosamine to the Artocarpus lectin are consistent with a simple single-step bimolecular association and unimolecular dissociation rate processes. The value of $K_{+1}$ and $K_{-1}$, at $21 ^oC$ are 8.1 X $10^5 M^{-1} s^{-1}$ and 50 $s^{-1}$, respectively. The activation parameters indicate an enthalpy-controlled association process.

Item Type:	Journal Article
Publication:	Journal of Biological Chemistry
Publisher:	American Society of Biological Chemists
Additional Information:	Copyright belongs to American Society of Biological Chemists.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	08 Jul 2008
Last Modified:	19 Sep 2010 04:46
URI:	http://eprints.iisc.ac.in/id/eprint/14710

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