Figure 8.

Cartoon of hypothesized Tg-induced structural alterations. (A) Insertion of the cis-5R,6S Tg lesion into the duplex opposite dA, in a Watson−Crick orientation, with the axial conformation of Tg⁶ CH₃, induces steric clash with the 5′ neighbor, G⁵. (B) Epimerization of the cis-5R,6S Tg lesion to the trans-5R,6R lesion allows the Tg⁶ CH₃ to assume an equatorial conformation that causes less steric interaction with Tg⁶ CH₃ and the G⁵ nucleotide. (C) Formation of a wobble Tg⁶•G¹⁹ base pair allows Tg⁶ to be displaced toward the major groove, resulting in less steric clash between the axial conformation of Tg⁶ CH₃ in the cis-5R,6S Tg configuration and the 5′-neighbor, G⁵.