Proton nuclear Overhauser effect study of the structure of an actinomycin D complex with a self-complementary tetranucleoside triphosphate

Saturation transfer and nuclear Overhauser effect (NOE) techniques have been used to assign some resonances of nonexchangeable protons in the NMR spectrum of the complex formed between actinomycin D and the self-complementary tetranucleoside triphosphate d(A-G-C-T). Intermolecular NOEs suggest that the drug chromophore intercalates between the two G-C base pairs of the nucleotide double helix, while the pentapeptide lactone rings fill the minor groove. Binding-induced distortions of helix geometry are discussed.