Nature Structural & Molecular Biology, Received 21 December 2013, Accepted11 July 2014, Published online10 August 2014, doi:10.1038/nsmb.2869

EF-G catalyzes tRNA translocation by disrupting interactions between decoding center and codon–anticodon duplex

Guangqiao Liu, Guangtao Song, Danyang Zhang, Dejiu Zhang, Zhikai Li, Zhixin Lyu, Jianshu Dong, John Achenbach, Weimin Gong, Xin Sheng Zhao, Knud H Nierhaus4, Yan Qin*(*corresponding author)

Abstract

During translation, ​elongation factor G (​EF-G) catalyzes the translocation of tRNA2–mRNA inside the ribosome. Translocation is coupled to a cycle of conformational rearrangements of the ribosomal machinery, and how ​EF-G initiates translocation remains unresolved. Here we performed systematic mutagenesis of Escherichia coli ​EF-G and analyzed inhibitory single-site mutants of ​EF-G that preserved pretranslocation (Pre)-state ribosomes with tRNAs in A/P and P/E sites (Pre–​EF-G). Our results suggest that the interactions between the decoding center and the codon–anticodon duplex constitute the barrier for translocation. Catalysis of translocation by ​EF-G involves the factor's highly conserved loops I and II at the tip of domain IV, which disrupt the hydrogen bonds between the decoding center and the duplex to release the latter, hence inducing subsequent translocation events, namely 30S head swiveling and tRNA2–mRNA movement on the 30S subunit

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