A Conserved Lysine Residue in the Crenarchaea-Specific Loop is Important for the Crenarchaeal Splicing Endonuclease Activity
A Conserved Lysine Residue in the Crenarchaea-Specific Loop is Important for the Crenarchaeal Splicing Endonuclease Activity
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DOI：
10.1016/j.jmb.2010.10.050
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发表时间：
2011-01-07
影响因子：
5.6
通讯作者：
Yoshinari, Shigeo
中科院分区：
文献类型：
--
作者：
Okuda, Maho;Shiba, Tomoo;Yoshinari, Shigeo
在大肠杆菌中，剪接核酸内切酶（EndA）识别并切割前体RNA以去除内含子。目前，EndAs根据其亚基结构分为三个家族：同源四聚体、同源二聚体和异源四聚体。根据结构亚基的大小，泉古菌异四聚体EndAs可以进一步分为两个亚科。亚家族A具有与催化亚基大小相似的结构亚基，而亚家族B具有显著小于催化亚基的结构亚基。在此之前，我们解决了来自Pyrobaculum aerophilum的EndA的晶体结构。该内切酶被归类为亚家族B，结构显示该酶在结构亚基中缺乏N-末端亚结构域。然而，没有结构信息可用于预测属于亚科A的泉古菌异源四聚体EndA。在此，我们报道了来自Aeropyrum pernix的EndA的晶体结构，推测其属于亚科A。该酶在结构亚基中具有N末端亚结构域，这表明异四聚体EndA的两个亚家族在结构上是不同的。从A到A pernix还拥有一个额外的环区，这是crenarchaeal EndAs的特征。我们的突变研究表明，保守的赖氨酸残基的环是重要的内切酶活性。此外，根据对接模型的环和对底物RNA的位置的序列特征促使我们提出，crenarchaea特定的环和一个额外的氨基酸序列的催化环的nanoarchaeal EndA是来自独立的趋同进化和功能，用于识别非典型的凸起螺旋凸起基序RNA作为底物。(c)2010爱思唯尔有限公司版权所有。
In Archaea, splicing endonuclease (EndA) recognizes and cleaves precursor RNAs to remove introns. Currently, EndAs are classified into three families according to their subunit structures: homotetramer, homodimer, and heterotetramer. The crenarchaeal heterotetrameric EndAs can be further classified into two subfamilies based on the size of the structural subunit. Subfamily A possesses a structural subunit similar in size to the catalytic subunit, whereas subfamily B possesses a structural subunit significantly smaller than the catalytic subunit. Previously, we solved the crystal structure of an EndA from Pyrobaculum aerophilum. The endonuclease was classified into subfamily B, and the structure revealed that the enzyme lacks an N-terminal subdomain in the structural subunit. However, no structural information is available for crenarchaeal heterotetrameric EndAs that are predicted to belong to subfamily A. Here, we report the crystal structure of the EndA from Aeropyrum pernix, which is predicted to belong to subfamily A. The enzyme possesses the N-terminal subdomain in the structural subunit, revealing that the two subfamilies of heterotetrameric EndAs are structurally distinct. EndA from A. pernix also possesses an extra loop region that is characteristic of crenarchaeal EndAs. Our mutational study revealed that the conserved lysine residue in the loop is important for endonuclease activity. Furthermore, the sequence characteristics of the loops and the positions towards the substrate RNA according to a docking model prompted us to propose that crenarchaea-specific loops and an extra amino acid sequence at the catalytic loop of nanoarchaeal EndA are derived by independent convergent evolution and function for recognizing noncanonical bulge-helix-bulge motif RNAs as substrates. (c) 2010 Elsevier Ltd. All rights reserved.