Kruklitis R, Nakai H
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D.C. 20007.
J Biol Chem. 1994 Jun 10;269(23):16469-77.
During bacteriophage Mu transposition, strand transfer is catalyzed in the presence of phage-encoded A and B proteins and Escherichia coli HU protein, attaching Mu ends to target DNA and creating an intermediate in transposition. Bacteriophage Mu A protein, which remains tightly bound to the Mu ends in the native strand-transfer intermediate, blocked initiation of Mu DNA replication by a system of 8 host proteins (DnaB helicase, DnaC protein, DnaG primase, DNA polymerase III holoenzyme, DNA polymerase I, DNA gyrase, DNA ligase, and single-strand binding protein). This 8-protein system had all enzymatic activities to convert the deproteinized intermediate to a cointegrate; however, additional host factor(s) were required to replicate the native intermediate. While replication of the native intermediate absolutely required DnaB helicase, DnaC protein, and DNA polymerase III holoenzyme, the specific requirements were relaxed for the deproteinized intermediate. Other host factors were able to replace these specific factors. These results indicate that Mu A protein, in conjunction with additional host factor(s), acts to promote assembly of specific host replication proteins at the Mu replication fork. This process may alter the stable interaction of Mu A protein with the ends to allow initiation of Mu DNA synthesis.
在噬菌体Mu转座过程中，链转移在噬菌体编码的A蛋白和B蛋白以及大肠杆菌HU蛋白存在的情况下被催化，将Mu末端连接到靶DNA上并产生转座中间体。噬菌体Mu A蛋白在天然链转移中间体中与Mu末端紧密结合，它通过一个由8种宿主蛋白组成的系统（DnaB解旋酶、DnaC蛋白、DnaG引物酶、DNA聚合酶III全酶、DNA聚合酶I、DNA回旋酶、DNA连接酶和单链结合蛋白）阻断Mu DNA复制的起始。这个由8种蛋白组成的系统具备将脱蛋白中间体转化为共整合体的所有酶活性；然而，复制天然中间体还需要其他宿主因子。虽然天然中间体的复制绝对需要DnaB解旋酶、DnaC蛋白和DNA聚合酶III全酶，但对于脱蛋白中间体，特定要求有所放宽。其他宿主因子能够替代这些特定因子。这些结果表明，Mu A蛋白与其他宿主因子共同作用，促进特定宿主复制蛋白在Mu复制叉处的组装。这个过程可能会改变Mu A蛋白与末端的稳定相互作用，从而允许Mu DNA合成的起始。
