Isolation, Macromolecular Properties, and Combining Site of a Chitooligosaccharide-specific Lectin from the Exudate of Ridge Gourd(Luffaa cutangzda)

Vellareddy, Anantharam and Patanjali, Sankhavaram R and Swam, Joginadha M and Sanadiq, Ashok R and Goldstein, Irwin J and Surolia, Avadhesha (1986) Isolation, Macromolecular Properties, and Combining Site of a Chitooligosaccharide-specific Lectin from the Exudate of Ridge Gourd(Luffaa cutangzda). In: Journal of Biological Chemistry, 261 (31). pp. 14621-14627.

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Abstract

A lectin specific for chito-oligosaccharides from the exudate of ridge gourd (Luffa acutangula) fruits has been purified to homogeneity by affinity chromatography. The lectin has a molecular weight of 48,000, an S(0)20,w of 4.06 S and a Stokes radius of 2.9 nm. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a single band corresponding to Mr of 24,000 was observed both in the presence and absence of beta-mercaptoethanol. The subunits in this dimeric lectin are, therefore, held together solely by noncovalent interactions. The lectin is not a glycoprotein, and secondary structure analysis by CD measurements showed 31% alpha-helix. The hemagglutinating activity of L. acutangula agglutinin was not inhibited by any of the monosaccharides tested. Among the disaccharides only di-N- acetylchitobiose was inhibitory. The inhibitory potency of chito- oligosaccharides increased dramatically with their size up to penta-N- acetylchitopentaose. The lectin has two binding sites for saccharides. The affinity of chito-oligosaccharides for L. acutangula lectin, as monitored by titrating the changes in the near UV-CD spectra and intrinsic fluorescence, increased strikingly with the number of GlcNAc units in them. The values of delta G, delta H, and delta S for the binding process showed a pronounced dependence on the size of the chito- oligosaccharides, indicating that the binding of higher oligomers is progressively more favored thermodynamically than di-N- acetylchitobiose. The thermodynamic data are consistent with an extended binding site in this lectin, which accommodates a tetrasaccharide.

Item Type:	Journal Article
Publication:	Journal of Biological Chemistry
Publisher:	American Society of Biological Chemists, Inc
Additional Information:	Copyright belongs to The American Society of Biological Chemists, Inc.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	26 Jun 2008
Last Modified:	19 Sep 2010 04:46
URI:	http://eprints.iisc.ac.in/id/eprint/14442

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