title: Guanine to inosine substitution leads to large increases in the population of a transient G·C Hoogsteen base pair.
abstract: We recently showed that Watson-Crick base pairs in canonical duplex DNA exist in dynamic equilibrium with G(syn)·C+ and A(syn)·T Hoogsteen base pairs that have minute populations of ∼1%. Here, using nuclear magnetic resonance R1ρ relaxation dispersion, we show that substitution of guanine with the naturally occurring base inosine results in an ∼17-fold increase in the population of transient Hoogsteen base pairs, which can be rationalized by the loss of a Watson-Crick hydrogen bond. These results provide further support for transient Hoogsteen base pairs and demonstrate that their population can increase significantly upon damage or chemical modification of the base.
authors.affiliation: Department of Integrative Structural and Computational Biology, The Scripps Research Institute , La Jolla, California 92037, United States.
authors.forename: Evgenia N
authors.initials: EN
authors.lastname: Nikolova
authors.forename: Frederick
authors.initials: F
authors.lastname: Stull
authors.forename: Hashim M
authors.initials: HM
authors.lastname: Al-Hashimi
mesh_terms: D020029:Base Pairing; D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D007288:Inosine / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation
chemical_list: D007288:Inosine; D006147:Guanine; D004247:DNA