Sub-Micellar Concentration of Sodium Dodecyl Sulphate Prevents Thermal Denaturation Induced Aggregation of Plant Lectin, Jacalin

The irreversible thermal unfolding of jacalin, the lectin purified from jackfruit seeds was accompanied by aggregation, where intermolecular interactions among the subunits are favoured over intramolecular interactions. The extent of aggregation increased as a function of temperature, time and protein concentration. The anionic surfactant, sodium dodecyl sulphate (SDS) significantly suppressed the formation of aggregates as observed by turbidity measurements and Rayleigh scattering assay. Moreover, far UV-CD spectra indicate that the protein β sheet transforms into α helical structure, when denatured in the presence of 3 mM SDS. Further, jacalin when heated in the presence of SDS partially retained the hemagglutination activity when jacalin-SDS mixture was diluted to 1:8 factor since 3 mM SDS was found to lyse the red blood cells. Thus, SDS only altered the aggregation behaviour of jacalin by preventing intermolecular hydrogen bonding among the exposed residues but did not completely stabilize the native conformation.