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首页> 外文期刊>Journal of Molecular Biology >Escherichia coli PriA helicase: Fork binding orients the helicase to unwind the lagging strand side of arrested replication forks
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Escherichia coli PriA helicase: Fork binding orients the helicase to unwind the lagging strand side of arrested replication forks

机译：大肠杆菌PriA解旋酶：叉结合使解旋酶定向，以解开被阻止的复制叉的落后链侧

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摘要

Escherichia coli PriA is a primosome assembly protein with 3' to 5' helicase activity whose apparent function is to promote resumption of DNA synthesis following replication-fork arrest. Here, we describe how initiation of helicase activity on DNA forks is influenced by both fork structure and by single-strand DNA-binding protein. PriA could recognize and unwind forked substrates where one or both arms were primarily duplex, and PriA required a small (two bases or larger) single-stranded gap at the fork in order to initiate unwinding. The helicase was most active on substrates with a duplex lagging-strand arm and a single-stranded leading-strand arm. On this substrate, PriA was capable of translocating on either the leading or lagging strands to unwind the duplex ahead of the fork or the lagging-strand duplex, respectively. Fork-specific binding apparently orients the helicase domain to unwind the lagging-strand duplex. Binding of single-strand-binding protein to forked templates could inhibit unwinding of the duplex ahead of the fork but not unwinding of the lagging-strand duplex or translocation on the lagging-strand template. While single-strand-binding protein could inhibit binding of PriA to the minimal, unforked DNA substrates, it could not inhibit PriA binding to forked substrates. In the cell, single-strand-binding protein and fork structure may direct PriA helicase to translocate along the lagging-strand template of forked structures such that the primosome is specifically assembled on that DNA strand.
机译：大肠杆菌PriA是具有3'至5'解旋酶活性的原核糖体组装蛋白，其表观功能是在复制叉被捕后促进DNA合成的恢复。在这里，我们描述了DNA叉子上解旋酶活性的启动如何受叉子结构和单链DNA结合蛋白的影响。 PriA可以识别和展开分叉的基材，其中一个或两个臂主要是双臂的，并且PriA需要在叉处有一个小（两个碱基或更大）的单链间隙才能启动退绕。解旋酶在带有双链落后链臂和单链领先链臂的底物上最活跃。在该底物上，PriA能够转移到前导链或滞后链上，从而分别在叉或滞后链双链体之前解链双链体。叉特异性结合显然使解旋酶结构域定向以解开落后链双链体。单链结合蛋白与叉状模板的结合可以抑制双链在叉之前的展开，但不能抑制后链双链的展开或在后链模板上的易位。虽然单链结合蛋白可以抑制PriA与最小的，未分叉的DNA底物的结合，但不能抑制PriA与分叉的底物的结合。在细胞中，单链结合蛋白和叉状结构可以指导PriA解旋酶沿着叉状结构的滞后链模板转移，从而使该DNA链上特异性地组装了初体。

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