ADCs Toxins, Pironetin is a potent inhibitor of tubulin. Pironetin covalently binds tubulin. Systematic alanine scanning shows, that the pironetin binding site was determined to be Lys352 of alpha-tubulin. Lys352 is located at the entrance of a small pocket of alpha-tubulin, and this pocket faces the beta-tubulin of the next dimer. This is the first compound that covalently binds to the alpha subunit of tubulin and Lys352 of alpha-tubulin and inhibits the interaction of tubulin heterodimers. HCT-116: IC50=0,002 uM; PSN1 : IC50=0,003 uM; T98G : IC50=15,43 uM; A549 : IC50=0,002 uM (preliminary laboratory results). Journal of Antibiotics (1996), 49, 173-180.