Circular dichroism and conformational transition of Dolichos biflorus and Robinia pseudoacacia lectins

The conformation of the lectins from Dolichos biflorus and Robinia pseudoacacia was studied by means of circular dichroism (CD). It was found that N-acetyl-D-galactosamine induced significant changes in the near-ultraviolet CD spectrum of Dolichos lectin but was ineffective with the lectin from Robinia. Tyrosine and tryptophan chromophores were chiefly involved in this saccharide-lectin interaction. The far-ultraviolet CD spectra indicated that both lectins have a significant content of the pleated sheet conformation, but not much, if any, alpha-helix. The predominant conformation in these lectins is the aperiodic bend structure which is stabilized chiefly by hydrophobic interactions. This was ascertained by the effect of sodium dodecylsulfate on these proteins.