ジャーナル: Mol Cell / 年: 2013 タイトル: Structure of an RNA silencing complex of the CRISPR-Cas immune system. 著者: Michael Spilman / Alexis Cocozaki / Caryn Hale / Yaming Shao / Nancy Ramia / Rebeca Terns / Michael Terns / Hong Li / Scott Stagg / 要旨: Bacterial and archaeal clustered regularly interspaced short palindromic repeat (CRISPR) loci capture virus and plasmid sequences and use them to recognize and eliminate these invaders. CRISPR RNAs ...Bacterial and archaeal clustered regularly interspaced short palindromic repeat (CRISPR) loci capture virus and plasmid sequences and use them to recognize and eliminate these invaders. CRISPR RNAs (crRNAs) containing the acquired sequences are incorporated into effector complexes that destroy matching invader nucleic acids. The multicomponent Cmr effector complex cleaves RNA targets complementary to the crRNAs. Here, we report cryoelectron microscopy reconstruction of a functional Cmr complex bound with a target RNA at ~12 Å. Pairs of the Cmr4 and Cmr5 proteins form a helical core that is asymmetrically capped on each end by distinct pairs of the four remaining subunits: Cmr2 and Cmr3 at the conserved 5' crRNA tag sequence and Cmr1 and Cmr6 near the 3' end of the crRNA. The shape and organization of the RNA-targeting Cmr complex is strikingly similar to the DNA-targeting Cascade complex. Our results reveal a remarkably conserved architecture among very distantly related CRISPR-Cas complexes.
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 93 K / 装置: FEI VITROBOT MARK IV 手法: Plasma clean grids for 5 seconds, apply 3 uL sample, and blot for 4 seconds before plunging.
Chain - #0 - Chain ID: A / Chain - #1 - Chain ID: C
ソフトウェア
名称: Chimera
詳細
Cmr2-Cmr3 crystal structure was fit into the EM density using the "fit in map" feature from Chimera. EM density corresponding to Cmr2-Cmr3 was segmented out. The Cmr2-Cmr3 structure was refined in the Cmr2-Cmr3 density map using MDFF with an EM scaling factor of 0.3 and implicit solvent.