Tanaka Yoshiyuki, Oda Shuji, Yamaguchi Hiroshi, Kudo Megumi, Kondo Yoshinori, Kojima Chojiro, Ono Akira
Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan.
Nucleic Acids Symp Ser (Oxf). 2006(50):47-8. doi: 10.1093/nass/nrl024.
Recently, it was reported that T-T mismatches can specifically recognize Hg(II), and form T-Hg(II)-T pairs. In order to understand the structure and properties of the T-Hg(II)-T pair, we measured NMR spectra for a DNA duplex, d(CGCGTTGTCC) x d(GGACTTCGCG), with two successive T-T mismatches (Hg(II)-binding sites) in the middle of the duplex. We identified imino proton resonances of the T-T mismatches in mercury-free duplex, and performed titration experiments with Hg(II) by using 1-dimensional (1D) (1)H NMR spectra. From the titration spectra, disappearances of imino proton signals were observed upon the addition of Hg(II). Furthermore, we observed additional signals of transient species, most likely mono-mercurated duplexes. This is an evidence that structural transformations between Hg(II)-free and Hg(II)-bound forms are slow enough for each species to give independent signals. These data strongly suggest that the imino protons of thymine bases were substituted with Hg(II), to form T-Hg(II)-T pairs in which one Hg(II) cross-links two N3 atoms of thymines.
最近，有报道称T-T错配能够特异性识别Hg(II)，并形成T-Hg(II)-T对。为了了解T-Hg(II)-T对的结构和性质，我们测量了一个DNA双链体d(CGCGTTGTCC)×d(GGACTTCGCG)的核磁共振谱，该双链体在中间位置有两个连续的T-T错配（Hg(II)结合位点）。我们确定了无汞双链体中T-T错配的亚氨基质子共振，并通过一维(1D) ¹H NMR谱对Hg(II)进行滴定实验。从滴定谱中可以观察到，加入Hg(II)后亚氨基质子信号消失。此外，我们还观察到了瞬态物种的额外信号，很可能是单汞化双链体。这证明了无Hg(II)形式和结合Hg(II)形式之间的结构转变足够缓慢，以至于每个物种都能给出独立的信号。这些数据有力地表明，胸腺嘧啶碱基的亚氨基质子被Hg(II)取代，形成了一个Hg(II)交联两个胸腺嘧啶N3原子的T-Hg(II)-T对。
