pUB110 DNA分子的紧密型结构

THE CONFORMATION OF THE COMPACT TYPE OF pUB110 DNA MOLECULE

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摘要经0.1%鸭血烯酸钠处理或经37℃溶菌酶作用的Bacillus subtilis BD366菌体,按碱法提取pUB110 DNA,可得到SC(超螺旋),OC(开环)和CT(Com-pact type,紧密型)结构的分子。SO和OC分子均可被EcoRⅠ,BamHⅠ和BglⅡ切成线状分子,但CT分子却不能。对pUB110DNA具有多切点的限制性内切酶Sau 3AⅠ对CT分子也不起作用。经86℃保温或沸水浴处理,CT分子能转变成SC和OC型,并可被Sau 3AⅠ酶切降解,推断CT结构可能是质粒的原始构型。 By using alkaline lysis method, the plasmid pUB110 of Bacillus subtilis BD366pretreated with an unsaturated fatty acid from duck serum was found in threeconformation types consisting of SC, OC and the dominant compact type (CT). TheCT molecules migrated faster than SC molecules in electrophoresis and appearedas compact masses under the electronmicroscope. pUB110 DNA with SC and OC con-formations can be cut by the restriction endonucleases EcoR I, BamH I and Bgl IIat single site and by Sau3AI at multiple sites, whereas pUB110 DNA with theCT conformation was resistant to EcoR I, BamH I, Bgl II and Sau 3AI. However,after treatment at 86℃ or in boiling water, CT could be digested with Sau 3AI andthe fragments produced were the same as those of the SC and OC molecules diges-ted with the same enzyme without treatment. It is suggested that the CT confor-mation could be the original type of the plasmid and switch to the SC or OC formsunder certain conditions.