No-go decay and nonstop decay are mRNA surveillance pathways that detect 
translational stalling and degrade the underlying mRNA, allowing the correct 
translation of the genetic code. In eukaryotes, the protein complex of Pelota 
(yeast Dom34) and Hbs1 translational GTPase recognizes the stalled ribosome 
containing the defective mRNA. Recently, we found that archaeal Pelota (aPelota) 
associates with archaeal elongation factor 1α (aEF1α) to act in the mRNA 
surveillance pathway, which accounts for the lack of an Hbs1 ortholog in 
archaea. Here we present the complex structure of aPelota and GTP-bound aEF1α 
determined at 2.3-Å resolution. The structure reveals how GTP-bound aEF1α 
recognizes aPelota and how aPelota in turn stabilizes the GTP form of aEF1α. 
Combined with the functional analysis in yeast, the present results provide 
structural insights into the molecular interaction between eukaryotic Pelota and 
Hbs1. Strikingly, the aPelota·aEF1α complex structurally resembles the 
tRNA·EF-Tu complex bound to the ribosome. Our findings suggest that the 
molecular mimicry of tRNA in the distorted "A/T state" conformation by Pelota 
enables the complex to efficiently detect and enter the empty A site of the 
stalled ribosome.