Two-dimensional NMR investigation of the binding of the anticancer drug actinomycin D to duplexed dATGCGCAT: Conformational features of the unique 2:1 adduct
- Emory Univ., Atlanta, GA (USA)
- Applied Biosystems, Foster City, CA (USA)
- Georgia State Univ., Atlanta (USA)
One- and two-dimensional NMR studied on the oligomer dA{sub 1}T{sub 2}G{sub 3}C{sub 4}G{sub 5}C{sub 6}A{sub 7}T{sub 8}, with and without actinomycin D (ActD), were conducted. Analysis of the NMR data, particularly 2D NOE intensities, revealed that the free oligonucleotide is a duplex in a standard right-handed B form. At the ratio of 1 ActD/duplex (R = 1), 1D NMR studies indicate that two 1:1 unsymmetric complexes form in unequal proportions with the phenoxazone ring intercalated at a GpC site, in agreement with previous studies. The 2D COSY data also confirm this interpretation. At R = 2, both COSY and NOESY spectra confirm the formation of a unique 2:1 species with C{sub 2} symmetry. The oligomer remains in a right-handed duplex but undergoes extreme conformational changes at and adjacent to the binding site. The deoxyribose conformation of T{sub 2}, C{sub 4}, and C{sub 6} shifts from primarily C2{prime}-endo in the free duplex to an increased amount of C3{prime}-endo in the 2:1 complex. This conformational change widens the minor groove and should help alleviate the steric crowding of the ActD peptides. In contrast to previous studies on ActD, the authors were able to distinguish the two peptide chains. The amino acid protons in the quinoid ring and benzenoid ring have significantly different chemical shifts. However, only the signals of the cyclic peptide pointing toward the center of the duplex and hence toward its equivalent peptide on the other, C{sub 2} related, ActD molecule had unusual shifts. The peptide interactions in this close-packed region may be responsible for the unique 2:1 species, for the negative cooperativity in binding, and for the conformational changes in the deoxyribsoe moieties.
- OSTI ID:
- 7193049
- Journal Information:
- Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 27:20; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
ACTINOMYCIN
ADDUCTS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
ANTIMITOTIC DRUGS
ANTINEOPLASTIC DRUGS
BIOCHEMISTRY
CHEMICAL SHIFT
CHEMISTRY
CONFORMATIONAL CHANGES
DNA ADDUCTS
DRUGS
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUCLEIC ACIDS
OLIGONUCLEOTIDES
ORGANIC COMPOUNDS
RESONANCE