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Biophys. J. BioFAST: First Published November 12, 2004. doi:10.1529/biophysj.104.051052
© 2004 by the Biophysical Society.

A more recent version of this article appeared on February 1, 2005.
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PROTEINS

Unfolding studies on Soybean agglutinin and Concanavalin A tetramers:A Comparative Account

Sharmistha Sinha 1, Nivedita Mitra 1, Gyanendra Kumar 1, Kanika Bajaj 1 and Avadhesha Surolia 1*

1 Molecular Biophysics Unit,Indian Institute of Science

* To whom correspondence should be addressed. E-mail: surolia{at}mbu.iisc.ernet.in.

Submitted on August 6, 2004
Revised on September 8, 2004
Accepted on 3 November 2004


  Abstract
The unfolding pathway of two very similar tetrameric legume lectins soybean agglutinin (SBA) and Concanavalin A (Con A) 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 DG of unfolding of SBA was much higher than Con A at all the temperatures at which the experiments were done. Con A had a Tg 18°C lesser than SBA. The higher conformational stability of SBA in comparison to Con A is largely due to substantial differences in their degrees of subunit interactions. Ionic interactions at the interface of the two proteins especially at the non-canonical interface seem to play a significant role in the observed stability differences between these two proteins. Further, SBA is a glycoprotein with a GlcNac2Man9 chain attached to Asn-75 of each subunit. The sugar chain in SBA lies at the non-canonical interface of the protein, and it is found to interact with the amino acid residues in the adjacent non-canonical interface. These interactions further stabilize SBA with respect to Con A, which is not glycosylated.

Key Words: Lectins, Protein Folding, Protein Stability, Quaternary Structure, Subunit Interactions, Two State Folding




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S. Sinha and A. Surolia
Attributes of Glycosylation in the Establishment of the Unfolding Pathway of Soybean Agglutinin
Biophys. J., January 1, 2007; 92(1): 208 - 216.
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S. Sinha and A. Surolia
Oligomerization Endows Enormous Stability to Soybean Agglutinin: A Comparison of the Stability of Monomer and Tetramer of Soybean Agglutinin
Biophys. J., June 1, 2005; 88(6): 4243 - 4251.
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Copyright © 2004 by the Biophysical Society.