ESCHERICHIA-COLI REPLICATION TERMINATION PROTEIN IMPEDES THE ACTION OF HELICASES
ESCHERICHIA-COLI REPLICATION TERMINATION PROTEIN IMPEDES THE ACTION OF HELICASES
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DOI：
10.1073/pnas.86.23.9104
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发表时间：
1989-12-01
影响因子：
11.1
通讯作者：
HORIUCHI, T
中科院分区：
文献类型：
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作者：
LEE, EH;KORNBERG, A;HORIUCHI, T
鉴定大肠杆菌复制终止（ter）的一致序列和分离ter结合蛋白（TBP）使我们能够在纯化的酶系统中测试它们对大肠杆菌染色体独特起源（oriC）启动的复制叉的影响。当提供纯化的TBP来结合它时，它在一个独特的方向上的复制受到严重阻碍。复制复合体内阻滞的目标现在可以归因于dna解旋酶在遇到TBP结合时无法分离双链。其他解旋酶，如rep和uvrD蛋白，在DNA上易位并使链向与DNA蛋白相反的方向移位，也会被阻断，但只有当tbp结合的蛋白方向相反时才会被阻断。从这些结果中，我们推断，ter的取向赋予了位于其上的TBP一个特定的极性，使得解旋酶从一侧面对TBP时被阻断，但当面对其另一侧时，可能通过取代TBP来起作用。因此，定向的TBP-ter复合物的内在性质负责阻碍解旋酶，而不是任何蛋白质-蛋白质相互作用。
Identification of the consensus sequence for termination of replication (ter) in Escherichia coli and the isolation of the ter-binding protein (TBP) allowed us to test their effects on replication forks initiated at the unique origin of the E. coli chromosome (oriC) in a purified enzyme system. Replication was severely impeded by ter in a unique orientation when purified TBP was supplied to bind it. The target for blockage within the replication complex can now be ascribed to the inability of dnaB helicase to separate the duplex strands when it encounters ter bound by TBP. Other helicases, such as rep and uvrD proteins, that translocate on DNA and displace strands in the direction opposite to that of dnaB protein are also blocked, but only when the TBP-bound ter is oriented in the other direction. From these results, we infer that the orientation of ter confers a particular polarity on the TBP seated on it, such that a helicase is blocked when it confronts TBP from one side, but can act, presumably by displacing TBP, when facing its other side. Thus, the intrinsic nature of the oriented TBP-ter complex is responsible for impeding the helicases, rather than any protein-protein interactions.