The CRISPR associated protein Cas4 Is a 5' to 3' DNA exonuclease with an iron-sulfur cluster.
The CRISPR associated protein Cas4 Is a 5' to 3' DNA exonuclease with an iron-sulfur cluster.
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DOI：
10.1371/journal.pone.0047232
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
White MF
中科院分区：
文献类型：
--
作者：
Zhang J;Kasciukovic T;White MF
Cas4蛋白是参与原核CRISPR系统抗病毒防御的核心CRISPR相关（Cas）蛋白之一。Cas4被认为在捕获新的病毒DNA序列以整合到宿主基因组中发挥作用。目前还没有报道Cas4的生化活性，但预计它包含一个RecB核酸酶结构域。我们在这里表明，来自古细菌Sulfolobus solfataricus的Cas4家族蛋白利用四个保守的半胱氨酸残基结合铁硫簇，其排列方式让人想起枯草芽孢杆菌的AddB核酸酶。Cas4家族蛋白Sso0001是一种体外5 ‘至3 ’单链DNA外切酶，被螺旋外DNA加合物阻滞。提出了Cas4在DNA双链切除中产生重组3 '单链DNA悬垂的作用。通过与Eubacterium rectales的相关细菌核酸酶的结构比较，发现铁硫簇可以被锌离子取代而不会破坏蛋白质结构，这对铁硫结合蛋白的进化具有重要意义。
The Cas4 protein is one of the core CRISPR-associated (Cas) proteins implicated in the prokaryotic CRISPR system for antiviral defence. Cas4 is thought to play a role in the capture of new viral DNA sequences for incorporation into the host genome. No biochemical activity has been reported for Cas4, but it is predicted to include a RecB nuclease domain. We show here that Cas4 family proteins from the archaeon Sulfolobus solfataricus utilise four conserved cysteine residues to bind an iron-sulfur cluster in an arrangement reminiscent of the AddB nuclease of Bacillus subtilis. The Cas4 family protein Sso0001 is a 5′ to 3′ single stranded DNA exonuclease in vitro that is stalled by extrahelical DNA adducts. A role for Cas4 in DNA duplex strand resectioning to generate recombinogenic 3′ single stranded DNA overhangs is proposed. Comparison of the AddB structure with that of a related bacterial nuclease from Eubacterium rectales reveals that the iron-sulfur cluster can be replaced by a zinc ion without disrupting the protein structure, with implications for the evolution of iron-sulfur binding proteins.
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