Funnell B E, Baker T A, Kornberg A
J Biol Chem. 1986 Apr 25;261(12):5616-24.
During enzymatic replication of plasmids containing the origin of the Escherichia coli chromosome, oriC, formation of an active initiation complex consisting of dnaA, dnaB, dnaC, and HU proteins, requires a supercoiled DNA template. Relaxed covalently closed plasmids are active only if supercoiled by gyrase prior to initiation; nicked and linear DNAs are inactive. Semi-conservative replication proceeds via delta structure as intermediates. Daughter molecules include nicked intermediates. Daughter molecules include nicked monomers and catenated pairs. Elongation is rapid, but late replicative intermediates accumulate because the final elongation and termination steps are slow. Production of covalently closed circular daughter DNA molecules requires removal of ribonucleotide residues (primers) by DNA polymerase I, assisted by ribonuclease H, gap filling, and ligation of nascent strands by ligase. Reconstitution of a complete cycle of oriC plasmid replication, beginning and ending with supercoiled molecules, has been achieved with purified proteins.
在含有大肠杆菌染色体复制起点oriC的质粒进行酶促复制过程中，由dnaA、dnaB、dnaC和HU蛋白组成的活性起始复合物的形成需要超螺旋DNA模板。松弛的共价闭环质粒只有在起始前被促旋酶超螺旋化时才具有活性；切口和线性DNA无活性。半保留复制通过δ结构作为中间体进行。子代分子包括切口中间体。子代分子包括切口单体和连环体对。延伸过程迅速，但后期复制中间体积累，因为最后的延伸和终止步骤缓慢。产生共价闭环子代DNA分子需要DNA聚合酶I在核糖核酸酶H的协助下去除核糖核苷酸残基（引物）、填补缺口并由连接酶连接新生链。利用纯化的蛋白质已实现了以超螺旋分子开始和结束的oriC质粒复制完整循环的重建。
