title: Hoogsteen versus Watson-Crick A-T basepairing in DNA complexes of a new group of 'quinomycin-like' antibiotics.
abstract: The interaction of a new group of 'quinomycin-like' antibiotics with the DNA duplexes d(ACGT)2 and d(GACGTC)2 has been investigated in solution by 1H NMR spectroscopy. By monitoring the intensity of intranucleotide base H6/H8 to deoxyribose H1'NOE cross-peaks we conclude that the terminal A-T basepairs flanking the CG bisintercalation site in the d(ACGT)2 complex adopt the Hoogsteen bonding scheme, with the purine base in a syn conformation. By comparison in the d(GACGTC)2 complex all glycosidic bond angles are anti, consistent with a preferred Watson-Crick basepairing scheme. Both DNA duplexes appear to be significantly unwound compared with the ligand-free DNAs. The data illustrate the influence of helical constraints on the stability of the Hoogsteen bonding scheme adjacent to the drug binding sites.
authors.affiliation: Peter MacCallum Cancer Institute NMR Facility, Victorian College of Pharmacy, Parkville, Australia.
authors.forename: M S
authors.initials: MS
authors.lastname: Searle
authors.forename: G
authors.initials: G
authors.lastname: Wickham
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004448:Echinomycin / Q000031:analogs & derivatives* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009690:Nucleic Acid Conformation
chemical_list: D000900:Anti-Bacterial Agents; C059307:UK 65662; D004448:Echinomycin; D004247:DNA