Enzymatic Incorporation of a Coumarin–Guanine Base Pair

Abstract

AbstractPrevious expansions beyond nature's preferred base‐pairing interactions have utilized either nonpolar shape‐fitting interactions or classical hydrogen bonding. Reported here is a hybrid of these systems. By replacing a single N−H with C−H at a Watson–Crick interface, the design space for new drug candidates and fluorescent nucleobase analogues is dramatically expanded, as demonstrated here by the new, highly fluorescent deoxycytidine mimic 3‐glycosyl‐5‐fluoro‐7‐methoxy‐coumarin‐2′‐deoxyribose (dCC). dGTP is selectively incorporated across from a template dCC during enzymatic DNA synthesis. Likewise, dCC is selectively incorporated across from a template guanine when dCC is provided as the triphosphate dCCTP. DNA polymerase I (Klenow fragment) exhibited about a 10‐fold higher affinity for dCCTP than dCTP, allowing selective incorporation of dCC in direct competition experiments. These results demonstrate that a single C−H can replace N−H at a Watson–Crick‐type interface with preservation of functional selectivity and enhanced activity.