title: Crystal structure of elongation factor 4 bound to a clockwise ratcheted ribosome.
abstract: Elongation factor 4 (EF4/LepA) is a highly conserved guanosine triphosphatase translation factor. It was shown to promote back-translocation of tRNAs on posttranslocational ribosome complexes and to compete with elongation factor G for interaction with pretranslocational ribosomes, inhibiting the elongation phase of protein synthesis. Here, we report a crystal structure of EF4-guanosine diphosphate bound to the Thermus thermophilus ribosome with a P-site tRNA at 2.9 angstroms resolution. The C-terminal domain of EF4 reaches into the peptidyl transferase center and interacts with the acceptor stem of the peptidyl-tRNA in the P site. The ribosome is in an unusual state of ratcheting with the 30S subunit rotated clockwise relative to the 50S subunit, resulting in a remodeled decoding center. The structure is consistent with EF4 functioning either as a back-translocase or a ribosome sequester.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA. Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8114, USA.
authors.forename: Matthieu G
authors.initials: MG
authors.lastname: Gagnon
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
authors.forename: Jinzhong
authors.initials: J
authors.lastname: Lin
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA. Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA.
authors.forename: David
authors.initials: D
authors.lastname: Bulkley
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA. Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8114, USA. Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA. thomas.steitz@yale.edu.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Steitz
mesh_terms: D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D010448:Peptide Initiation Factors; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000737:chemistry; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry*; D016963:Thermus thermophilus; D035602:Transcriptional Elongation Factors / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; C515651:LepA protein, E coli; D010448:Peptide Initiation Factors; D035602:Transcriptional Elongation Factors; D012343:RNA, Transfer
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