Renaturated ricin toxin B chain made in Escherichia coli is soluble, stable, and biologically active

Escherichia coli cells transformed with plasmids containing ricin B-chain coding sequences are shown to express this heterologous protein in inclusion bodies. After denaturation and renaturation of the product in the presence of glutathione and lactose, the recombinant ricin B-chain is soluble, biologically active and stable. Cytotoxicity of heterodimer with this protein and ricin A-chain is bound to be only ten times less than of native ricin. Recombinant B-chain alone was nontoxic to cells (ID50 > 10(-6)M). Our data suggest that N-glycosylation of ricin B-chain is not required for its biological activity.