title: Structures of modified eEF2 80S ribosome complexes reveal the role of GTP hydrolysis in translocation.
abstract: On the basis of kinetic data on ribosome protein synthesis, the mechanical energy for translocation of the mRNA-tRNA complex is thought to be provided by GTP hydrolysis of an elongation factor (eEF2 in eukaryotes, EF-G in bacteria). We have obtained cryo-EM reconstructions of eukaryotic ribosomes complexed with ADP-ribosylated eEF2 (ADPR-eEF2), before and after GTP hydrolysis, providing a structural basis for analyzing the GTPase-coupled mechanism of translocation. Using the ADP-ribosyl group as a distinct marker, we observe conformational changes of ADPR-eEF2 that are due strictly to GTP hydrolysis. These movements are likely representative of native eEF2 motions in a physiological context and are sufficient to uncouple the mRNA-tRNA complex from two universally conserved bases in the ribosomal decoding center (A1492 and A1493 in Escherichia coli) during translocation. Interpretation of these data provides a detailed two-step model of translocation that begins with the eEF2/EF-G binding-induced ratcheting motion of the small ribosomal subunit. GTP hydrolysis then uncouples the mRNA-tRNA complex from the decoding center so translocation of the mRNA-tRNA moiety may be completed by a head rotation of the small subunit.
authors: Howard Hughes Medical Institute, Health Research Inc.,Wadsworth Center, Albany, NY 12201-0509, USA.
authors: Derek J
authors: DJ
authors: Taylor
authors: Jakob
authors: J
authors: Nilsson
authors: A Rod
authors: AR
authors: Merrill
authors: Gregers Rom
authors: GR
authors: Andersen
authors: Poul
authors: P
authors: Nissen
authors: Joachim
authors: J
authors: Frank
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D001203:Ascomycota / Q000378:metabolism; D020285:Cryoelectron Microscopy / Q000379:methods; D006160:Guanosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020652:Peptide Elongation Factor 2 / Q000737:chemistry* / Q000378:metabolism; D020653:Peptide Elongation Factor G / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034443:RNA Transport; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D020652:Peptide Elongation Factor 2; D020653:Peptide Elongation Factor G; D012333:RNA, Messenger; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D012343:RNA, Transfer