Adenine frequently pairs with the Hoogsteen edge of an oxidized guanine base (8OG) causing G to T transversions. The (syn)8OG:dA base pair is indistinguishable from the cognant base pair and can be extended by DNA polymerases with reduced efficiency. To examine the structural basis of this reduced efficiency, we sought to obtain the structure of the “product” complex of DNA polymerase (pol) β with the (syn)8OG:dA base pair at the primer terminus by soaking the binary complex crystals with a hydrolysable dCTP analogue complementary to the template base G. Crystallographic refinement of the structure revealed that the adenine of the (syn)8OG:dA base pair had been expelled from the primer terminus and a dCMP was inserted opposite 8OG in a reverse orientation; another uninserted molecule of the analogue was bound to the templating base G. This leads to an abortive complex that could form the basis of oxidatively-induced pol β stalling.

腺嘌呤经常与氧化鸟嘌呤碱基（8OG）的Hoogsteen边缘配对，从而导致G到T的转化。（syn）8 OG：dA碱基对与同源碱基对没有区别，并且可以被DNA聚合酶以降低的效率延伸。为了检查这种降低效率的结构基础，我们试图通过将二元复合晶体浸泡在引物末端来获得DNA聚合酶（pol）β与（syn）8OG：dA碱基对的“产物”复合物的结构。与模板碱基G互补的可水解dCTP类似物。晶体学上的细化显示，（syn的腺嘌呤）8OG：dA碱基对已从引物末端去除，并在8OG对面以相反方向插入dCMP; 另一个未插入类似物的分子与模板碱基G结合。这导致了流产复合物，该复合物可形成氧化诱导的polβ失速的基础。