Fazakerley G V, Gdaniec Z, Sowers L C
Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Sacaly, Gif-sur-Yvette, France.
J Mol Biol. 1993 Mar 5;230(1):6-10. doi: 10.1006/jmbi.1993.1119.
We have examined the base-pairing properties of N4-methoxycytosine (mo4C), a mutagenic base analog, in DNA by nuclear magnetic resonance spectroscopy. Unlike standard bases, the tautomeric equilibrium of mo4C could be strongly influenced by base-pair formation. Paired with A, mo4C is found predominantly in the imino configuration in Watson-Crick geometry. However, when paired with G, two structurally distinct configurations are observed in equilibrium with one another. In one configuration, mo4C is in the amino form paired with G in Watson-Crick geometry. In the second species, mo4C is in the imino configuration paired with G in a wobble geometry. This is the first demonstration of basepair induced tautomeric shifts in DNA and supports the hypothesis that rare tautomeric forms may be involved in mutagenesis.
