A conjugate of the A1 peptide of cholera toxin and the lectin of Wisteria floribunda that activates the adenylate cyclase of intact cells.

The active A1 peptide of cholera toxin was linked by a disulphide bond to the lectin of Wisteria floribunda. The resulting conjugate activated the adenylate cyclase of intact U937 or K562 cells at the same concentrations as native toxin did, but to a greater extent. Activation was inhibited by N-acetyl-D-galactosamine or by antisera to the lectin or peptide. The characteristic lag phase between addition of toxin to cells and activation of cyclase was not found with the conjugate or with free A1 peptide.