Unfolding Studies on Soybean Agglutinin and Concanavalin A Tetramers: A Comparative Account

Sinha, Sharmistha and Mitra, Nivedita and Kumar, Gyanendra and Bajaj, Kanika and Surolia, Avadhesha (2004) Unfolding Studies on Soybean Agglutinin and Concanavalin A Tetramers: A Comparative Account. In: Biophysics Journal, 88 . pp. 1300-1310.

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Abstract

The unfolding pathway of two very similar tetrameric legume lectins soybean agglutinin (SBA) and Concanavalin A (ConA) were determined using GdnCl-induced denaturation. Both proteins displayed a reversible two-state unfolding mechanism. The analysis of isothermal denaturation data provided values for conformational stability of the two proteins. It was found that the ${\triangle}G$ of unfolding of SBA was much higher than ConA at all the temperatures at which the experiments were done. ConA had a $T_g$ $18{^\circ}C$ less than SBA. The higher conformational stability of SBA in comparison to ConA is largely due to substantial differences in their degrees of subunit interactions. Ionic interactions at the interface of the two proteins especially at the noncanonical interface seem to play a significant role in the observed stability differences between these two proteins. Furthermore, SBA is a glycoprotein with a $GlcNac_2Man_9$ chain attached to Asn-75 of each subunit. The sugar chain in SBA lies at the noncanonical interface of the protein, and it is found to interact with the amino acid residues in the adjacent noncanonical interface. These interactions further stabilize SBA with respect to ConA, which is not glycosylated.

Item Type:	Journal Article
Publication:	Biophysics Journal
Publisher:	Biophysics Society
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	20 Feb 2006
Last Modified:	19 Sep 2010 04:23
URI:	http://eprints.iisc.ac.in/id/eprint/5410

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