A molecular mousetrap determines polarity of termination of DNA replication in E-coli
A molecular mousetrap determines polarity of termination of DNA replication in E-coli
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DOI：
10.1016/j.cell.2006.04.040
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发表时间：
2006-06-30
期刊：
影响因子：
64.5
通讯作者：
Dixon, Nicholas E.
中科院分区：
文献类型：
--
作者：
Mulcair, Mark D.;Schaeffer, Patrick M.;Dixon, Nicholas E.
在大肠杆菌的染色体合成过程中，复制叉被Tus结合的Ter位点从一个方向而不是另一个方向阻断。为了研究这种极性的基础，我们测量了Tus从分叉的TerB寡核苷酸的解离速率，例如由复制型DnaB解旋酶在Ter位点的分叉阻断（非允许）和允许末端产生的解离速率。在允许末端的几个核苷酸的链分离足以迫使Tus快速解离以允许叉进展。相反，链分离延伸到并包括严格保守的G-C（6）碱基对在非允许端导致形成一个稳定的锁定复合物。锁的形成特别需要胞嘧啶残基C（6）。锁定复合物的晶体结构表明，C（6）从其正常位置移动14埃，结合在Tus表面上的乙酰胆碱特异性口袋中。
During chromosome synthesis in Escherichia coli, replication forks are blocked by Tus bound Ter sites on approach from one direction but not the other. To study the basis of this polarity, we measured the rates of dissociation of Tus from forked TerB oligonucleotides, such as would be produced by the replicative DnaB helicase at both the fork-blocking (nonpermissive) and permissive ends of the Ter site. Strand separation of a few nucleotides at the permissive end was sufficient to force rapid dissociation of Tus to allow fork progression. In contrast, strand separation extending to and including the strictly conserved G-C(6) base pair at the nonpermissive end led to formation of a stable locked complex. Lock formation specifically requires the cytosine residue, C(6). The crystal structure of the locked complex showed that C(6) moves 14 angstrom from its normal position to bind in acytosine-specific pocket on the surface of Tus.