Binding of methylumbelliferyl N-acetyl-fl-D-glucopyranoside and 4-methylumbelliferyl N,N' - diacetyl- beta-chitobioside to rice lectin: studies by equilibrium dialysis and fluorescence quenching titrations

Indravathamma, Poola and Navin Kumar, D. Kella (1986) Binding of methylumbelliferyl N-acetyl-fl-D-glucopyranoside and 4-methylumbelliferyl N,N' - diacetyl- beta-chitobioside to rice lectin: studies by equilibrium dialysis and fluorescence quenching titrations. Biochirnica et Biophvsica Acta , 882. 12 -17.

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Abstract

The binding of two fluorescent sugars 4-methylumbelliferyl N-acetyl-fl-D-glucopyranoside (MeUmbGIcNAc) and 4-methylumbelliferyl N,N'-diacetyl-fl-chitobioside (MeUmb(GlcNAc)2) to rice lectin was studied by equilibrium dialysis and extrinsic fluorescence titrations. Rice lectin contains four identical and independent carbohydrate binding sites per 36000 M r protein. Equilibrium dialysis experiments at 25°C gave an association constant value of (4.82 + 0.32). 104 M-i whereas fluorescence quenching titrations at 15°C yielded a value of (8.17 + 0.25)-104 M -! with MeUmbGlcNAc. The relative fluorescence quenching efficiency of the sugar increased with the saccharide chain length. The calculated quenching of fluorescence in both cases was I00%, indicating that the sugar binding site on the lectin is hydrophobic in nature. Binding constants and thermodynamic parameters of the binding of MeUmb glycosides were determined at I0, 15, 20 and 25°C. In both cases, binding constants decreased with increasing temperature, indicating that the binding of sugar to the lectin is exothermic in nature. The AH ° and AS ° values for MeUmbGlcNAc-rice lectin interaction were - 8.51 kcal • mol - i and - 7.07 e.u., respectively, and for that of MeUmb(GlcNAc) 2- rice lectin the corresponding values were - 11.89 kcal • mol - t and - 16.72 e.u.

Item Type:	Article
Uncontrolled Keywords:	Rice lectin, Binding studies, affinity chromatography, Carbohydrate binding; Lectin; Equilibrium dialysis; Fluorescence quenching
Subjects:	500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 13 Carbohydrate Chemistry
Divisions:	Protein Chemistry and Technology
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	04 Mar 2011 09:38
Last Modified:	28 Dec 2011 10:22
URI:	http://ir.cftri.res.in/id/eprint/9993

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