Li Z, Tamura P J, Wilkinson A S, Harris C M, Harris T M, Stone M P
Department of Chemistry and Center in Molecular Toxicology, Vanderbilt University, Nashville, Tennessee 37235, USA.
Biochemistry. 2001 Jun 12;40(23):6743-55. doi: 10.1021/bi002785r.
The structure of the bay region (1R,2S,3R,4S)-N6-[1-(1,2,3,4-tetrahydro-2,3,4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl adduct at X(7) of 5'-d(CGGACAXGAAG)-3'.5'-d(CTTCTTGTCCG)-3', incorporating codons 60, 61 (underlined), and 62 of the human N-ras protooncogene, was determined by NMR. This was the bay region benz[a]anthracene RSRS (61,3) adduct. The BA moiety intercalated above the 5'-face of the modified base pair. NOE connectivities between imino protons were disrupted at T16 and T17. Large chemical shifts at the lesion site were consistent with ring current shielding arising from the BA moiety. A large chemical shift dispersion was observed for the BA aromatic protons. An increased rise of 8.17 A was observed between base pairs A6 x T17 and X7 x T(16). The PAH moiety stacked with the purine ring of A6, the 5'-neighbor nucleotide. This resulted in buckling of the 5'-neighbor A6 x T17 base pair, evidenced by exchange broadening for the T17 imino resonance. It also interrupted sequential NOE connectivities between nucleotides C5 and A6. The A6 deoxyribose ring showed an increased percentage of the C3'-endo conformation. This differed from the bay region BA RSRS (61,2) adduct, in which the lesion was located at position X6 [Li, Z., Mao, H., Kim, H.-Y., Tamura, P. J., Harris, C. M., Harris, T. M., and Stone, M. P. (1999) Biochemistry 38, 2969-2981], but was similar to the benzo[a]pyrene BP SRSR (61,3) adduct [Zegar I. S., Chary, P., Jabil, R. J., Tamura, P. J., Johansen, T. N., Lloyd, R. S., Harris, C. M., Harris, T. M., and Stone, M. P. (1998) Biochemistry 37, 16516-16528]. The altered sugar pseudorotation at A6 appears to be common to both bay region BA RSRS (61,3) and BP SRSR (61,3) adducts. It could not be discerned if the C3'-endo conformation at A6 in the BA RSRS (61,3) adduct altered base pairing geometry at X7 x T16, as compared to the C2'-endo conformation. The structural studies suggest that the mutational spectrum of this adduct may be more complex than that of the BA RSRS (61,2) adduct.
通过核磁共振确定了5'-d(CGGACAXGAAG)-3'.5'-d(CTTCTTGTCCG)-3'中(1R,2S,3R,4S)-N6-[1-(1,2,3,4-四氢-2,3,4-三羟基苯并[a]蒽基)]-2'-脱氧腺苷加合物在X(7)处的湾区结构，该结构包含人类N-ras原癌基因的密码子60、61（下划线部分）和62。这是湾区苯并[a]蒽RSRS(61,3)加合物。BA部分插入到修饰碱基对5'-面的上方。在T16和T17处，亚氨基质子之间的NOE连接性被破坏。损伤位点处的大化学位移与BA部分产生的环电流屏蔽一致。观察到BA芳香族质子有很大的化学位移分散。在碱基对A6 x T17和X7 x T(16)之间观察到8.17 Å的增加上升。多环芳烃部分与5'-相邻核苷酸A6的嘌呤环堆积。这导致5'-相邻A6 x T17碱基对发生弯曲，T17亚氨基共振的交换加宽证明了这一点。它还中断了核苷酸C5和A6之间的连续NOE连接性。A6脱氧核糖环显示出C3'-内型构象的百分比增加。这与湾区BA RSRS(61,2)加合物不同，在后者中损伤位于X6位置[Li, Z., Mao, H., Kim, H.-Y., Tamura, P. J., Harris, C. M., Harris, T. M., and Stone, M. P. (1999) Biochemistry 38, 2969 - 2981]，但与苯并[a]芘BP SRSR(61,3)加合物相似[Zegar I. S., Chary, P., Jabil, R. J., Tamura, P. J., Johansen, T. N., Lloyd, R. S., Harris, C. M., Harris, T. M., and Stone, M. P. (1998) Biochemistry 37, 16516 - 16528]。A6处糖假旋转的改变似乎是湾区BA RSRS(61,3)和BP SRSR(61,3)加合物共有的。与C2'-内型构象相比，无法辨别BA RSRS(61,3)加合物中A6处的C3'-内型构象是否改变了X7 x T16处的碱基配对几何结构。结构研究表明，该加合物的突变谱可能比BA RSRS(61,2)加合物更复杂。
