Circular dichroism studies on the effects of sodium dodecyl sulfate on the conformation of some phytohemagglutinins

Abstract

Conformation and conformational transitions of phytohemagglutinins (lectins) from Arachis hypogaea (peanut), Lens culinaris (lentil), Glycine max (soybean), and Ricinus communis (castor bean) were studied by the circular dichroism probe. The lectins were found to possess a high amount of the pleated sheet (β) conformation. The tertiary structure and main chain conformation of the lectins were disorganized by sodium dodecyl sulfate (SDS) and the main chain was reconstructed by relatively high concentrations of SDS (weight ratio of SDS to protein about 5–8 to 1) into new orders of higher helix content than in the native protein. More helix was formed in acid solutions than in nearly neutral solutions. The disorganization of the native tertiary structure by SDS was expressed in a decrease of the circular dichroism bands related to the tyrosine and tryptophan chromophores and in appearance of the vibronic fine structure in the phenylalanine band zone. The tertiary structure of the L. culinaris and R. communis lectins was more sensitive to SDS than the tertiary structure of the two other lectins.