Structure of yeast Argonaute with guide RNA.
Nakanishi, K., Weinberg, D.E., Bartel, D.P., Patel, D.J.(2012) Nature 486: 368-374
- PubMed: 22722195 
- DOI: https://doi.org/10.1038/nature11211
- Primary Citation of Related Structures:  
4F1N - PubMed Abstract: 
The RNA-induced silencing complex, comprising Argonaute and guide RNA, mediates RNA interference. Here we report the 3.2 Å crystal structure of Kluyveromyces polysporus Argonaute (KpAGO) fortuitously complexed with guide RNA originating from small-RNA duplexes autonomously loaded by recombinant KpAGO. Despite their diverse sequences, guide-RNA nucleotides 1-8 are positioned similarly, with sequence-independent contacts to bases, phosphates and 2'-hydroxyl groups pre-organizing the backbone of nucleotides 2-8 in a near-A-form conformation. Compared with prokaryotic Argonautes, KpAGO has numerous surface-exposed insertion segments, with a cluster of conserved insertions repositioning the N domain to enable full propagation of guide-target pairing. Compared with Argonautes in inactive conformations, KpAGO has a hydrogen-bond network that stabilizes an expanded and repositioned loop, which inserts an invariant glutamate into the catalytic pocket. Mutation analyses and analogies to ribonuclease H indicate that insertion of this glutamate finger completes a universally conserved catalytic tetrad, thereby activating Argonaute for RNA cleavage.
Organizational Affiliation: 
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.