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The crystal structure of lambda-Gam protein suggests a model for RecBCD inhibition

机译:Lambda-Gam蛋白的晶体结构提示RecBCD抑制模型

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In Escherichia coli, RecBCD processes double-stranded DNA breaks during the initial stages of homologous recombination. RecBCD contains helicase and nuclease activities, and unwinds and digests the blunt-ended DNA until a specific eight-nucleotide sequence, Chi, is encountered. Chi modulates the nuclease activity of RecBCD and results in a resected DNA end, which is a substrate for RecA during subsequent steps in recombination. RecBCD also acts as a defence mechanism against bacteriophage infection by digesting linear viral DNA present during virus replication or resulting from the action of restriction endonucleases. To avoid this fate, bacteriophage lambda encodes the gene Gam whose product is an inhibitor of RecBCD. Gam has been shown to bind to RecBCD and inhibit its helicase and nuclease activities. We show that Gam inhibits RecBCD by preventing it from binding DNA. We have solved the crystal structure of Gam from two different crystal forms. Using the published crystal structure of RecBCD in complex with DNA we suggest models for the molecular mechanism of Gam-mediated inhibition of RecBCD. We also propose that Gam could be a mimetic of single-stranded, and perhaps also double-stranded, DNA. (c) 2007 Elsevier Ltd. All rights reserved.
机译:在大肠杆菌中,RecBCD在同源重组的初始阶段处理双链DNA断裂。 RecBCD包含解旋酶和核酸酶活性,展开并消化平末端DNA,直到遇到特定的8个核苷酸序列Chi。 Chi调节RecBCD的核酸酶活性,并导致切除的DNA末端,这是在重组的后续步骤中RecA的底物。 RecBCD还通过消化病毒复制过程中存在的线性病毒DNA或限制性核酸内切酶的作用而产生的抗噬菌体感染的防御机制。为了避免这种命运,噬菌体λ编码基因Gam,其产物是RecBCD的抑制剂。 Gam已显示与RecBCD结合并抑制其解旋酶和核酸酶活性。我们表明,Gam通过阻止RecBCD与DNA结合来抑制RecBCD。我们已经从两种不同的晶体形式解析出Gam的晶体结构。使用与DNA复合的RecBCD的晶体结构,我们建议建立Gam介导的RecBCD抑制的分子机制模型。我们还提出,Gam可以是单链甚至双链DNA的模拟物。 (c)2007 Elsevier Ltd.保留所有权利。

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