title: EF4 disengages the peptidyl-tRNA CCA end and facilitates back-translocation on the 70S ribosome.
abstract: EF4 catalyzes tRNA back-translocation through an unknown mechanism. We report cryo-EM structures of Escherichia coli EF4 in post- and pretranslocational ribosomes (Post- and Pre-EF4) at 3.7- and 3.2-Å resolution, respectively. In Post-EF4, peptidyl-tRNA occupies the peptidyl (P) site, but the interaction between its CCA end and the P loop is disrupted. In Pre-EF4, the peptidyl-tRNA assumes a unique position near the aminoacyl (A) site, denoted the A site/EF4 bound (A/4) site, with a large displacement at its acceptor arm. Mutagenesis analyses suggest that a specific region in the EF4 C-terminal domain (CTD) interferes with base-pairing between the peptidyl-tRNA 3'-CCA and the P loop, whereas the EF4 CTD enhances peptidyl-tRNA interaction at the A/4 site. Therefore, EF4 induces back-translocation by disengaging the tRNA's CCA end from the peptidyl transferase center of the translating ribosome.
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Dejiu
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Kaige
authors.initials: K
authors.lastname: Yan
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Guangqiao
authors.initials: G
authors.lastname: Liu
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Guangtao
authors.initials: G
authors.lastname: Song
authors.affiliation: Key Laboratory of Protein and Peptide Pharmaceuticals, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jiejian
authors.initials: J
authors.lastname: Luo
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Erchao
authors.initials: E
authors.lastname: Cheng
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Wu
authors.affiliation: Key Laboratory of Protein and Peptide Pharmaceuticals, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Taijiao
authors.initials: T
authors.lastname: Jiang
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Lou
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
mesh_terms: D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034443:RNA Transport; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism*; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C515651:LepA protein, E coli; D010448:Peptide Initiation Factors; D012346:RNA, Transfer, Amino Acyl; C019037:tRNA, peptidyl-
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