Mukhopadhyay G, Carr K M, Kaguni J M, Chattoraj D K
Laboratory of Biochemistry, National Cancer Institute, NIH, Bethesda, MD 20892.
EMBO J. 1993 Dec;12(12):4547-54. doi: 10.1002/j.1460-2075.1993.tb06143.x.
Replication of P1 plasmid requires both the plasmid-specific initiator, RepA, and the host initiator, DnaA. Here we show that DnaA can make the P1 origin reactive to the single-strand specific reagents KMnO4 and mung bean nuclease. Addition of RepA further increased the KMnO4 reactivity of the origin, although RepA alone did not influence the reaction. The increased reactivity implies that the two initiators interact in some way to alter the origin conformation. The KMnO4 reactivity was restricted to one strand of the origin. We suggest that the roles of DnaA in P1 plasmid and bacterial replication are similar: origin opening and loading of the DnaB helicase. The strand-bias in chemical reactivity at the P1 origin most likely indicates that only one of the strands is used for the loading of DnaB, a scenario consistent with the unidirectional replication of the plasmid.
P1 质粒的复制需要质粒特异性起始蛋白 RepA 和宿主起始蛋白 DnaA。在此我们表明，DnaA 可使 P1 复制起点对单链特异性试剂高锰酸钾（KMnO4）和绿豆核酸酶产生反应。添加 RepA 进一步增强了复制起点对 KMnO4 的反应性，尽管单独的 RepA 并不影响该反应。反应性的增强意味着这两种起始蛋白以某种方式相互作用以改变复制起点的构象。KMnO4 的反应性仅限于复制起点的一条链。我们认为，DnaA 在 P1 质粒复制和细菌复制中的作用相似：打开复制起点并加载 DnaB 解旋酶。P1 复制起点化学反应性的链偏向很可能表明只有一条链用于加载 DnaB，这一情况与质粒的单向复制一致。
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