Carbohydrate binding specificity of the $T_n$-antigen binding lectin from Vicia villosa seeds $(VVLB_4)$

Puri, Kamal Deep and Gopalakrishnan, B and Avadhesha, Surolia (1992) Carbohydrate binding specificity of the $T_n$-antigen binding lectin from Vicia villosa seeds $(VVLB_4)$. In: FEBS Letters, 312 (2-3). pp. 208-212.

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Abstract

2-Dansylamino-2-deoxy-D-galactose (GalNDns) is a useful fluorescent probe to study the interaction of non-fluorescent sugars with the $B_4$ lectin from Vicia villosa seed; $(VVLB_4)$. Binding of the lectin to GalNDns leads to a 5.2-fold increase in Dansyl fluorescence with a concomitant 10 nm blue shift in its emission maximum. The strong binding of GalNDns $(K_u = 7.33 \times 104 M^- \hspace {2mm} at 20^0C)$ is due to a favourable entropic contribution to the association process. Among the other sugars studied, GalNAc$\alpha$l-O-Ser followed by Me$\alpha$GalNAc are the best ligands. 2-Deoxygalactose, galactosamine and galactose are 2013, 469 and 130 times weaker ligands, respectively, as compared to GalNAc, whereas GalNDns is about 2.44 times more potent than GalNAc, indicating that substitutions at the C-2 position of GalNAc have a considerable influence on the binding affinities. Equatorial orientation of the hydroxyl group at C-3 and axial orientation at C-4 as in galactose are important for the interaction with $VVLB_4$. The C-6 hydroxyl group is not indispensable. The binding site of the lectin is directed exclusively towards monosaccharides alone. Interestingly enough, despite its preference for Me$\alpha$GalNAc over Me$\beta$GalNAc, in oligosaccharides, the lectin prefers terminal $\beta$-linked GalNAc as compared to the $\alpha$-linked one.

Item Type:	Journal Article
Publication:	FEBS Letters
Publisher:	Elsevier Science B.V.
Additional Information:	Copyright of this article belongs to Elsevier Science B.V.
Keywords:	Vicia villosa lectin;2-Dansylamino-2-deoxy-Image-galactose;Monosaccharide binding;Orientation of hydroxyl group
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	14 Feb 2008
Last Modified:	19 Sep 2010 04:42
URI:	http://eprints.iisc.ac.in/id/eprint/12804

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