Probing conformational transitions towards mutagenic Watson-Crick-like G·T mismatches using off-resonance sugar carbon R1ρ relaxation dispersion.
Journal Article (Journal Article)
NMR off-resonance R1ρ relaxation dispersion measurements on base carbon and nitrogen nuclei have revealed that wobble G·T/U mismatches in DNA and RNA duplexes exist in dynamic equilibrium with short-lived, low-abundance, and mutagenic Watson-Crick-like conformations. As Watson-Crick-like G·T mismatches have base pairing geometries similar to Watson-Crick base pairs, we hypothesized that they would mimic Watson-Crick base pairs with respect to the sugar-backbone conformation as well. Using off-resonance R1ρ measurements targeting the sugar C3' and C4' nuclei, a structure survey, and molecular dynamics simulations, we show that wobble G·T mismatches adopt sugar-backbone conformations that deviate from the canonical Watson-Crick conformation and that transitions toward tautomeric and anionic Watson-Crick-like G·T mismatches restore the canonical Watson-Crick sugar-backbone. These measurements also reveal kinetic isotope effects for tautomerization in D2O versus H2O, which provide experimental evidence in support of a transition state involving proton transfer. The results provide additional evidence in support of mutagenic Watson-Crick-like G·T mismatches, help rule out alternative inverted wobble conformations in the case of anionic G·T-, and also establish sugar carbons as new non-exchangeable probes of this exchange process.
- Rangadurai, A; Szymanski, ES; Kimsey, I; Shi, H; Al-Hashimi, HM
- September 2020
Volume / Issue
- 74 / 8-9
Start / End Page
- 457 - 471
Pubmed Central ID
Electronic International Standard Serial Number (EISSN)
Digital Object Identifier (DOI)