Intercalation of the (1R,2S,3R,4S)-N6-[1-(1,2,3,4- Tetrahydro-2,3,4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl Adduct in the N-ras Codo

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• 作者：Zhijun Li ; Pamela J. Tamura ; Amanda S. Wilkinson ; Constance M. Harris ; Thomas M. Harris ; and Michael P. Stone
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：June 12, 2001
• 年：2001
• 卷：40
• 期：23
• 页码：6743 - 6755
• 全文大小：477K
• 年卷期：v.40,no.23(June 12, 2001)
• ISSN：1520-4995

文摘

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 X⁷ of 5'-d(CGGACAXGAAG)-3'·5'-d(CTTCTTGTCCG)-3', incorporating codons 60, 61 (underlined), and 62 of the human N-ras protooncogene, was determinedby NMR. This was the bay region benz[a]anthracene RSRS (61,3) adduct. The BA moiety intercalatedabove the 5'-face of the modified base pair. NOE connectivities between imino protons were disrupted atT¹⁶ and T¹⁷. Large chemical shifts at the lesion site were consistent with ring current shielding arisingfrom the BA moiety. A large chemical shift dispersion was observed for the BA aromatic protons. Anincreased rise of 8.17 Å was observed between base pairs A⁶·T¹⁷ and X⁷·T¹⁶. The PAH moiety stackedwith the purine ring of A⁶, the 5'-neighbor nucleotide. This resulted in buckling of the 5'-neighbor A⁶·T¹⁷base pair, evidenced by exchange broadening for the T¹⁷ imino resonance. It also interrupted sequentialNOE connectivities between nucleotides C⁵ and A⁶. The A⁶ deoxyribose ring showed an increasedpercentage of the C3'-endo conformation. This differed from the bay region BA RSRS (61,2) adduct, inwhich 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 alteredsugar 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·T¹⁶, as compared to the C2'-endo conformation. The structuralstudies suggest that the mutational spectrum of this adduct may be more complex than that of the BARSRS (61,2) adduct.