Chen F M
Department of Chemistry, Tennessee State University, Nashville 37209-1561.
Nucleic Acids Res. 1988 Mar 25;16(5):2269-81. doi: 10.1093/nar/16.5.2269.
Effects of A:T base pairs on the propensity of B to Z conformational transitions have been investigated by the CD salt titrations on d(CG)5' d(GC)5' terminal or central A:T replaced decamers, and terminal A:T appended dodecamers. The presence of A:T at the center greatly inhibits the B to Z transition of both G:C decamers. Moderate Z inhibitions are shown by terminal A:T replacements and additions to d(CG)5' with the former exhibiting a stronger effect. In contrast, the addition and replacement with A:T at the terminals of d(GC)5 facilitate the B to Z conversion, with the replacement exhibiting a somewhat more pronounced effect. These results may be rationalized in terms of the number of contigous CG sequences present in an oligomer and the relative inhibitory effects of other dinucleotide sequences. Our results also suggest that some short oligomers with purine at the 5'-end, such as d[A(CG)nT] with n greater than or equal to 2, may likely crystallize as Z conformations.
通过对 d(CG)5'd(GC)5' 末端或中心 A:T 替换的十聚体以及末端添加 A:T 的十二聚体进行圆二色光谱盐滴定，研究了 A:T 碱基对 B 向 Z 构象转变倾向的影响。中心存在 A:T 极大地抑制了两种 G:C 十聚体从 B 向 Z 的转变。末端 A:T 替换和添加到 d(CG)5' 时表现出适度的 Z 抑制作用，前者效果更强。相比之下，在 d(GC)5' 的末端添加和替换 A:T 促进了 B 向 Z 的转变，替换的效果更为明显。这些结果可以根据寡聚物中连续 CG 序列的数量以及其他二核苷酸序列的相对抑制作用来解释。我们的结果还表明，一些 5' 端带有嘌呤的短寡聚物，如 n 大于或等于 2 的 d[A(CG)nT]，可能会以 Z 构象结晶。
