title: Binding of AR-1-144, a tri-imidazole DNA minor groove binder, to CCGG sequence analyzed by NMR spectroscopy.
abstract: The interactions of N-[2-(dimethylamino)ethyl]-1-methyl-4-[1-methyl-4-[4-formamido-1-meth ylimidazole-2-carboxamido]imidazole-2-carboxamido]imidazole-2-c arboxa mide (AR-1-144), a tri-imidazole polyamide minor groove binder, with DNA have been investigated by NMR and CD spectroscopy. A series of DNA oligonucleotides with a C/G-containing four-bp core, i.e. CCGG, CGCG, GGCC, and GCGC, have been titrated with AR-1-144 at different ratios. AR-1-144 favors the CCGG sequence. The flanking sequence of the CCGG core also influences the binding preference, with a C or T being favored on the 3'-side of the CCGG core. The three-dimensional structure of the symmetric 2:1 side-by-side complex of AR-1-144 and GAACCGGTTC, determined by NOE-constrained NMR refinement, reveals that each AR-1-144 binds to four base pairs, i.e. at C5-G6-G7-T8, with every amide-imidazole unit forming two potential hydrogen bonds with DNA. The same DNA binding preference of AR-1-144 was also confirmed by circular dichroism spectroscopy, indicating that the DNA binding preference of AR-1-144 is independent of concentration. The cooperative binding of an AR-1-144 homodimer to the (purine)CCGG(pyrimidine) core sequence appears to be weaker than that of the distamycin A homodimer to A/T sequences, most likely due to the diminished hydrophobic interactions between AR-1-144 and DNA. Our results are consistent with previous footprinting data and explain the binding pattern found in the crystal structure of a di-imidazole drug bound to CATGGCCATG.
authors.affiliation: Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: X L
authors.initials: XL
authors.lastname: Yang
authors.forename: C
authors.initials: C
authors.lastname: Kaenzig
authors.forename: M
authors.initials: M
authors.lastname: Lee
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D019281:Dimerization; D004214:Distamycins / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*
chemical_list: C121196:AR-1-144; D004214:Distamycins; D009838:Oligodeoxyribonucleotides; D004247:DNA