Interactions among iron(II) bleomycin, Lewis bases, and DNA.

The interaction of sulfur-containing ligands with complexes of Fe(II) bleomycin [Fe(II)Blm] was investigated by comparing DNA strand-scission activity with the structural characteristics of the complex. The bithiazole ring of excess Blm can form intermolecular complexes with Fe(II)Blm and with NO-Fe(II)Blm, and the bithiazole groups of CO-Fe(II)Blm interact with the metal center. This binding can be reversed by glutathione, CO-Fe(II)Blm binds to poly(dA-dT) . poly(dA-dT) via its bithiazole group to change the environment of the Fe2+ ion. Glutathione binds to the CO-Fe(II)Blm-poly(dA-dT) . poly(dA-dT) complex under conditions in which it stimulates DNA strand scission by Fe(II)Blm.