22 ブレオマイシンによるDNA塩基配列の認識と切断機構(口頭発表の部)
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DNA serves as a target for the action of small molecules including natural antibiotics and designed synthetic molecules. These molecules bind directry to DNA, in some cases with sequence-specific manner, and cause DNA strand brekage by metal ions dependent reaction. Current interests for the action of these molecules concern with the chemical mechanisms of their sequence-specific recognition and degradation of DNA. Bleomycin, a family of glycopeptide-derived antibiotics, mediate degradation of DNA by metal ions such as Fe(II) and oxygen dependent reaction preferentially at the pyrimidine of 5'-GC-3' and 5'-GT-3' recognition sites. Bithiazole group is considered to play a key role for the BLM binding to double-helical DNA, while its binding mode has not yet been well understood. A critical question is whether bithiazole grop can recognize GC and GT sequences. Photo-BLM and lumi-BLM, which were obtained by selective photo-rearrangement at 2,4'-bithiazole group of BLM to 4,4'-bithiazole and thiazolyl-isothiazole groups, respectively, were shown to degradate DNA at the same sequences as BLM does. Since photo- and lumi-BLMs retain a common positioning of two ring nitrogens in their hetero-aromatic rings and BLMs show the strong affinities to guanine residue in DNA, one interpretation is that the interaction between the guanine and the ring nitrogen(s) may control the sequence specificity in DNA cleaving or binding mode of BLMs. To examine the role of N-2 amino group of guanine residue, we synthesized the oligodeoxynucleotides replacing the G-C base pairs with I-C base pairs. Inosine, like guanine, base pairs with cytosine, but it lacks an N-2 amino group that could protrude into the minor groove of double-helical B-DNA. The question is whether inosine can effect to the cleavage reaction by BLMs. DNA cleavage reactions by these photochemically modified BLMs and the possible interaction between guanine N-2 amino group and BLMs will be discussed.
- 天然有機化合物討論会の論文
- 1987-07-25
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