Chaotropes trigger conformational rearrangements differently in Concanavalin A

Abstract

Concanavalin A (ConA) is a plant lectin having industrial and biological applications. Concanavalin A changes conformation upon exposure to different stress conditions, like exposure to sodium dodecyl sulphate, guanidine hydrochloride, varying hydronium ion potential, etc. The conformational changes were studied using circular dichroism spectroscopy and the structural rigidity of ConA was explored using fluorescence spectroscopy, taking tryptophan as an intrinsic and 8-anilino-1-naphthalenesulfonic acid as an extrinsic fluorescence probes, in different stress conditions. ConA loses the quaternary structure in all the studied stress conditions, which further leads to denaturation of the protein. However, the mechanism of denaturation varied with the studied conditions, like different SDS concentrations and hydronium ion potentials, wherein the protein undergoes a conformational rearrangement from $$\upbeta $$ -sheet to $$\upalpha $$ -helix. Moreover, GdnHCl triggered complete denaturation of ConA into a predominantly random coil conformation. The results suggested that denaturation of ConA follows different pathways depending on the chemical properties and concentrations of the denaturants used. SynopsisGuanidine hydrochloride shows complete unfolding of Concanavalin A (Con A) above 2 M concentration, whereas GdnHCl between 1–2 M triggered the molten globule-like conformation. At basic pH, ConA adopts all- $$\upbeta $$ -sheet conformation, and at acidic pH it retained demetallized monomeric jelly roll motif. Additionally, in the presence of SDS at >2 mM, ConA undergoes conformational rearrangement into a predominantly $$\upalpha $$ -helix conformation, rather a leticn-like all- $$\upbeta $$ -sheet conformation at lower concentrations of SDS.