Fagan P A, Fàbrega C, Eritja R, Goodman M F, Wemmer D E
Department of Chemistry, University of California at Berkeley, 94720, USA.
Biochemistry. 1996 Apr 2;35(13):4026-33. doi: 10.1021/bi952657g.
DNA polymerase makes errors by misincorporating natural DNA bases and base analogs. Because of the wide variety of possible mismatches and the varying efficiency with which they are repaired, structural studies are necessary to understand in detail how these mispairs differ and can be distinguished from standard Watson-Crick base pairs. 2-Aminopurine (AP) is a highly mutagenic base analog. The objective of this study was to determine the geometry of the AP x C mispair in DNA at neutral pH. Although several studies have focused on the AP x C mispair in DNA, there is not as of yet consensus on its structure. At least four models have been proposed for this mispair. Through the use of NMR spectroscopy with selective 15N-labeling of exocyclic amino nitrogens on bases of interest, we are able to resolve ambiguities in previous studies. We find here that, in two different DNA sequences, the AP x C mispair at neutral and high pH is in a wobble geometry. The structure and stability of this base mispair is dependent upon the local base sequence.
DNA聚合酶会因错误掺入天然DNA碱基和碱基类似物而产生错误。由于可能的错配种类繁多，且修复效率各不相同，因此需要进行结构研究，以详细了解这些错配如何不同，以及如何与标准的沃森-克里克碱基对区分开来。2-氨基嘌呤（AP）是一种高度诱变的碱基类似物。本研究的目的是确定中性pH条件下DNA中AP x C错配的几何结构。尽管有几项研究聚焦于DNA中的AP x C错配，但其结构尚未达成共识。针对这种错配至少提出了四种模型。通过使用对感兴趣碱基上的环外氨基氮进行选择性15N标记的核磁共振光谱，我们能够解决先前研究中的模糊问题。我们在此发现，在两种不同的DNA序列中，中性和高pH条件下的AP x C错配呈摆动几何结构。这种碱基错配的结构和稳定性取决于局部碱基序列。
