title: Imidazole-imidazole pair as a minor groove recognition motif for T:G mismatched base pairs.
abstract: The T:G mismatched base pair is associated with many genetic mutations. Understanding its biological consequences may be aided by studying the structural perturbation of DNA caused by a T:G base pair and by specific probing of the mismatch using small molecular ligands. We have shown previously that AR-1-144, a tri-imidazole (Im-Im-Im) minor groove binder, recognizes the sequence CCGG. NMR structural analysis of the symmetric 2:1 complex of AR-1-144 and GAACCGGTTC revealed that each AR-1-144 binds to four base pairs with the guanine N2 amino group forming a bifurcated hydrogen bond to a side-by-side Im/Im pair. We predicted that the free G-N2 amino group in a T:G wobble base pair can form two individual hydrogen bonds to a side-by-side Im/Im pair. Thus an Im/Im pair may be a good recognition motif for a T:G base pair in DNA. Cooperative and tight binding of an AR-1-144 homodimer to GAACTGGTTC permits a detailed structural analysis by 2D NOE NMR refinement and the refined structure confirms our prediction. Surprisingly, AR-1-144 does not bind to GAATCGGTTC. We further show that both the Im-Im-Im/Im-Py-Im heterodimer and the Im-Im-Im/Im-Im-Im homodimer bind strongly to the CACGGGTC + GACTCGTG duplex. These results together suggest that an Im/Im pair can specifically recognize a single T:G mismatch. Our results may be useful in future design of molecules (e.g. linked dimers) that can recognize a single T:G mismatch with specificity.
authors.affiliation: Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: X L
authors.initials: XL
authors.lastname: Yang
authors.forename: R B
authors.initials: RB
authors.lastname: Hubbard
authors.forename: M
authors.initials: M
authors.lastname: Lee
authors.forename: Z F
authors.initials: ZF
authors.lastname: Tao
authors.forename: H
authors.initials: H
authors.lastname: Sugiyama
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
mesh_terms: D020137:Base Pair Mismatch / Q000235:genetics*; D020029:Base Pairing; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D006150:Guanine Nucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D009584:Nitrogen / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D011522:Protons; D013379:Substrate Specificity; D013942:Thymine Nucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017186:Titrimetry
chemical_list: D006150:Guanine Nucleotides; D007093:Imidazoles; D008024:Ligands; D011522:Protons; D013942:Thymine Nucleotides; C029899:imidazole; D004247:DNA; D009584:Nitrogen