The structure of the CRISPR-associated protein Csa3 provides insight into the regulation of the CRISPR/Cas system.
The structure of the CRISPR-associated protein Csa3 provides insight into the regulation of the CRISPR/Cas system.
复制标题
DOI：
10.1016/j.jmb.2010.11.019
复制
发表时间：
2011-01-28
影响因子：
5.6
通讯作者：
Lawrence CM
中科院分区：
文献类型：
--
作者：
Lintner NG;Frankel KA;Tsutakawa SE;Alsbury DL;Copié V;Young MJ;Tainer JA;Lawrence CM
适应性免疫系统最近已在原核生物中被认识到，在原核生物中，为了响应病毒感染，它们将入侵者衍生的DNA的短片段整合到称为规则间隔短回文重复序列（CRISPR）的基因座中。在随后的感染中，CRISPR基因座被转录并加工成指导序列，用于中和入侵的RNA或DNA。CRISPR相关蛋白机制（Cas）是这一过程的核心，但CRISPR/Cas系统的许多分子细节仍有待阐明。在这里，我们报告了Csa 3的第一个结构，Csa 3是一种来自硫磺硫化叶菌（Sso 1445）的CRISPR相关蛋白，它揭示了一种二聚体双结构域蛋白。N-末端结构域是二核苷酸结合结构域上的独特变异，其协调二聚体形成。此外，它利用两个保守的序列基序（Thr-h-Gly-Phe-（Asn/Asp）-Glu-X4-Arg和Leu-X2-Gly-h-Arg）在二聚体轴上构建一个2倍对称口袋。这个口袋很可能代表一个调节配体结合位点。N-末端结构域与C-末端MarR样翼螺旋-转角-螺旋结构域融合，预期其参与DNA识别。总的来说，Csa 3的独特结构域架构表明在N-末端结构域的变构控制下的转录调节因子。或者，Csa 3可以在更大的复合物中发挥作用，保守的裂缝参与蛋白质-蛋白质或蛋白质-核酸相互作用。在Csx 1中也发现了类似的N端结构域，Csx 1是第二个功能未知的CRISPR相关蛋白家族。
Adaptive immune systems have recently been recognized in prokaryotic organisms where, in response to viral infection, they incorporate short fragments of invader-derived DNA into loci called Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs). In subsequent infections, the CRISPR loci are transcribed and processed into guide sequences for the neutralization of the invading RNA or DNA. The CRISPR-associated protein machinery (Cas) lies at the heart of this process, yet many of the molecular details of the CRISPR/Cas system remain to be elucidated. Here we report the first structure of Csa3, a CRISPR-associated protein from Sulfolobus solfataricus (Sso1445), which reveals a dimeric two-domain protein. The N-terminal domain is a unique variation on the di-nucleotide binding-domain that orchestrates dimer formation. In addition, it utilizes two conserved sequence motifs (Thr-h-Gly-Phe-(Asn/Asp)-Glu-X4-Arg and Leu-X2-Gly-h-Arg) to construct a 2-fold symmetric pocket on the dimer axis. This pocket is likely to represent a regulatory ligand-binding site. The N-terminal domain is fused to a C-terminal MarR-like winged helix-turn-helix domain that is expected to be involved in DNA recognition. Overall, the unique domain architecture of Csa3 suggests a transcriptional regulator under allosteric control of the N-terminal domain. Alternatively, Csa3 may function in a larger complex, with the conserved cleft participating in protein-protein or protein-nucleic acid interactions. A similar N-terminal domain is also identified in Csx1, a second CRISPR associated protein family of unknown function.