Selective Association between a Macrocyclic Nickel Complex and Extrahelical Guanine Residues

详细信息    查看全文

• 作者：Hui-Chen Shih ; Helina Kassahun ; Cynthia J. Burrows ; and Steven E. Rokita
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：November 9, 1999
• 年：1999
• 卷：38
• 期：45
• 页码：15034 - 15042
• 全文大小：161K
• 年卷期：v.38,no.45(November 9, 1999)
• ISSN：1520-4995

文摘

Nickel-dependent recognition and oxidation of guanine have been linked in part through theparamagnetic effects of nickel on the NMR of model oligonucleotide duplexes. Direct interaction betweennickel and guanine N7 had originally been postulated from correlations between the efficiency of guanineoxidation and the environment surrounding its N7 position. ¹H and ³¹P NMR spectra of DNA containinga single, isolated extrahelical guanine are consistent with selective binding of nickel to the N7 of thisunique base over a background of nonspecific association to the phosphate backbone. The presence of amacrocyclic complex or simple salt of nickel did not detectably alter the structure of the duplex orextrahelical residue. Accordingly, nickel appeared to bind the extrahelical guanine N7 within the majorgroove as indicated by paramagnetic effects on the proton signals of nucleotides on the 5' but not 3' sideof the nickel binding site. Similar ¹H NMR analysis of DNA containing a dynamic equilibrium ofextrahelical guanine residues also suggested that the nickel complex did not affect the native distributionof structures. Oxidation of these sites by a nickel-mediated pathway consequently reflected their solventaccessibility in a general and metal-independent manner. The close proximity of the extrahelical guaninesproduced a composite of paramagnetic effects on each adjacent nucleotide resulting from both direct andproximal coordination of nickel.