2012年5月24日,美国冷泉港实验室结构生物学家Leemor Joshua-Tor等报道了hAgo2(human Argonaute-2)与miR-20a( microRNA-20a )复合体高分辨率的晶体结构,该研究成果发表在最新一期的Cell上。
AGO蛋白(Argonaute proteins)是RNA引导的沉默复合体(RNA-Induced Silencing Complex ,RISC)的核心元件,用于引导小RNA识别靶标。原核AGO 蛋白(argonaute proteins) 由N 末端,PAZ,MID 和PIWI4个结构域组成。
研究发现,人AGO蛋白的总体结构与结构域组成与原核AGO蛋白基本一致。还发现,miRNA锚定在mid和PAZ结构域末端,在结合槽(binding groove)形成k-turn 。
更加有趣的是,miRNA的结合显著提高了hAgo2的稳定性,使其能保持稳定的蛋白构象。
此研究为理解Ago2在发育和疾病发生中的功能提供了框架。(生物谷Bioon.com)
doi:10.1016/j.cell.2012.05.017
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PMID:
The Structure of Human Argonaute-2 in Complex with miR-20a
Elad Elkayam,Claus-D. Kuhn,Ante Tocilj,Astrid D. Haase,Emily M. Greene,Gregory J.Hannon,and Leemor Joshua-Tor
Argonaute proteins lie at the heart of the RNA-Induced Silencing Complex (RISC), wherein they use small RNA guides to recognize targets. Prior studies established the architecture of Argonaute proteins and revealed a crescent-shaped base made up of the amino-terminal, PAZ,middle,and PIWI domains; however, these studies were based on prokaryotic Argonaute proteins of unclearbiochemical and biological function. Here we report the crystal structure of human Argonaute-2 bound to microRNA-20a at 2.2 ? resolution. Overall architecture and domain organization is shared with its prokaryotic counterparts, although hAgo2′s PAZ domain is further removed from other domains. The miRNA is anchored at both ends by the mid- and PAZ domains but makes several kinks and turns along the binding groove. Interestingly, miRNA binding confers remarkable stability on hAgo2, locking this otherwise flexible enzyme into a stable conformation. Our findings provide a framework to understand the functions of Ago2 in essential processes in development and disease.