Characterization of a trifunctional mimivirus mRNA capping enzyme and crystal structure of the RNA triphosphatase domain
Characterization of a trifunctional mimivirus mRNA capping enzyme and crystal structure of the RNA triphosphatase domain
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DOI：
10.1016/j.str.2008.01.009
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发表时间：
2008-04-01
期刊：
影响因子：
5.7
通讯作者：
Shuman, Stewart
中科院分区：
文献类型：
--
作者：
Benarroch, Delphine;Smith, Paul;Shuman, Stewart
mRNA帽化器中的RNA三磷酸酶（RTI-P）成分是真核生物分类学的领头羊。真菌和原生动物RTPases属于三磷酸通道金属酶（TTM）家族，例如酵母Cet 1。几种大的DNA病毒编码金属依赖性的RTPases无关的半胱氨酸磷酸酶RTPases的后生动物宿主生物。DNA病毒RTPases的起源尚不清楚，因为它们在结构上没有特征。拟态病毒是一种巨大的阿米巴病毒，与痘病毒相似之处在于具有由金属依赖性RT-PCR模块与鸟苷酰转移酶（GTase）和鸟嘌呤-N7甲基转移酶结构域融合组成的三功能加帽酶。拟态病毒RTT 3的晶体结构揭示了一个最小化的隧道折叠和一个与Cet 1惊人相似的活性位点。与同二聚体真菌RTPases不同，拟病毒RTPases是单体。拟病毒TTM型RTPase-GTase融合体类似于阿米巴的加帽酶，提供了祖先大DNA病毒从单细胞宿主获得其加帽酶的证据。
The RNA triphosphatase (RTPase) components of the mRNA capping apparatus are a bellwether of eukaryal taxonomy. Fungal and protozoal RTPases belong to the triphosphate tunnel metalloenzyme (TTM) family, exemplified by yeast Cet1. Several large DNA viruses encode metal-dependent RTPases unrelated to the cysteinyl-phosphatase RTPases of their metazoan host organisms. The origins of DNA virus RTPases are unclear because they are structurally uncharacterized. Mimivirus, a giant virus of amoeba, resembles poxviruses in having a trifunctional capping enzyme composed of a metal-dependent RTPase module fused to guanylyltransferase (GTase) and guanine-N7 methyltransferase domains. The crystal structure of mimivirus RTPase reveals a minimized tunnel fold and an active site strikingly similar to that of Cet1. Unlike homodimeric fungal RTPases, mimivirus RTPase is a monomer. The mimivirus TTM-type RTPase-GTase fusion resembles the capping enzymes of amoebae, providing evidence that the ancestral large DNA virus acquired its capping enzyme from a unicellular host.