A DNA-BINDING ANTITUMOR ANTIBIOTIC BINDS TO SPECTRIN

Aureolic acid group of antibiotics inhibit transcription by reversible binding to DNA in presence of divalent magnesium. We for the first ti me report binding of the one of such antitumor antibiotic, mithramycin (MTR), to the major protein component of erythrocyte cytoskeleton, sp ectrin. A reasonably high apparent dissociation constant was estimated to be 1.5 mu M. The binding of mithramycin in the absence of any diva lent cation to the large cytoskeletal protein led to quenching in the tryptophan fluorescence of the protein, Stern-Volmer quenching of the tryptophan residues by acrylamide revealed conformational change in th e MTR-bound spectrin. This preliminary study might be useful in unders tanding other possible sites of actions after translocation. (C) 1995 Academic Press, Inc.