[Obtaining and characterization of the B-chains of mistletoe toxic lectins]

Mistletoe toxic lectins consist of two polypeptide chains: an enzymatic A chain, the toxic component, is joined by disulfide bond to a B chain conferring the lectin properties to the complete molecules. Mistletoe leaves contain three of toxic lectins encoded by three genes. The three B chains were produced in Escherichia coli in a soluble form. The recombinant proteins were found to bind to asialofetuin but in contrast to native proteins could be competed to a less extent by simple sugars D-galactose and N-acetyl-D-galactosamine. The functional properties of the proteins were strongly influenced by storage conditions such as salt concentration and simple sugar presence thus indicating an unstable folding. The lectin activity of one of the recombinant B chains was most close to the native protein that possibly results from the absence of N-glycosylation.