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Thermodynamics of interaction of caffeic acid and quinic acid with multisubunit proteins

Suryaprakash, P. and Kumar, Ramesh P. and Prakash, V. (2000) Thermodynamics of interaction of caffeic acid and quinic acid with multisubunit proteins. International Journal of Biological Macromolecules, 27. pp. 219-228.

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Helianthinin is a multisubunit protein from Sunflower seeds. Caffeic acid (CA) and quinic acid (QA) are intrinsic ligands present in sunflower seeds. The mechanism of interaction of these ligands with multisubunit proteins is limited. The present study enables one to understand the mechanism of the interaction of these ligands with the protein helianthinin. From this study, it is shown that CA has two classes of binding sites on helianthinin. The high-affinity class of sites total six from 60910 for both high-affinity and low-affinity sites. Tryptophan, tyrosine and lysine residues of the protein are mainly involved in the interaction with CA. The temperature dependence of the binding in the range 10–45°C can be clearly described by an enthalpy–entropy compensation effect at the low-affinity class of sites, while it is described by positive ΔCop at the high-affinity class of sites. This positive DCp o has a contribution to the protein stability. The binding strength of CA also has a positive cooperativity at higher protein concentration. QA has two classes of binding sites on the protein based on the strength of the interaction. The interaction of QA with the protein is predominantly described by positive ΔCop for both classes of affinity. This suggests predominance of ionic:hydrogen bonding in the interaction process. Differential scanning calorimetric measurements reveal that the binding of both CA and QA induces destabilisation of the subunit–subunit interaction. Human methaemoglobin (mHb) has two binding sites on the molecule for CA. Both CA and QA decrease the stability of mHb, as indicated by decreased Tm. This destabilisation is also accompanied by dissociation to the monomers with concomitant conformational changes.

Item Type: Article
Uncontrolled Keywords: Caffeic acid; Quinic acid; Helianthinin; Human methaemoglobin
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 29 Protein Chemistry
600 Technology > 08 Food technology > 19 Lipids-oils/fats > Sunflower Seed
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 28 Jun 2007 12:05
Last Modified: 28 Dec 2011 09:28
URI: http://ir.cftri.com/id/eprint/1277

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