Jaworski A, Hsieh W T, Blaho J A, Larson J E, Wells R D
Department of Biochemistry, School of Medicine, University of Alabama, Birmingham 35294.
Science. 1987 Nov 6;238(4828):773-7. doi: 10.1126/science.3313728.
Left-handed DNA is shown to exist and elicit a biological response in Escherichia coli. A plasmid encoding the gene for a temperature-sensitive Eco RI methylase (MEco RI) was cotransformed with different plasmids containing inserts that had varying capacities to form left-handed helices or cruciforms with a target Eco RI site in the center or at the ends of the inserts. Inhibition of methylation in vivo was found for the stable inserts with the longest left-handed (presumably Z) helices. In vitro methylation with the purified MEco RI agreed with the results in vivo. Supercoil-induced changes in the structure of the primary helix in vitro provided confirmation that left-handed helices were responsible for this behavior. The presence in vivo of left-handed inserts elicits specific deletions and plasmid incompatibilities in certain instances.
已证明左手螺旋DNA存在并能在大肠杆菌中引发生物学反应。一个编码温度敏感型Eco RI甲基化酶（MEco RI）基因的质粒与不同质粒共转化，这些质粒含有插入片段，这些插入片段形成左手螺旋或十字形结构的能力各不相同，靶标Eco RI位点位于插入片段的中心或末端。对于具有最长左手（推测为Z）螺旋的稳定插入片段，发现其体内甲基化受到抑制。用纯化的MEco RI进行的体外甲基化与体内结果一致。体外超螺旋诱导的初级螺旋结构变化证实了左手螺旋是导致这种行为的原因。在某些情况下，体内左手螺旋插入片段的存在会引发特定的缺失和质粒不相容性。
