title: Arrangement of tRNAs in pre- and posttranslocational ribosomes revealed by electron cryomicroscopy.
abstract: The three-dimensional structure of the translating 70S E. coli ribosome is presented in its two main conformations: the pretranslocational and the posttranslocational states. Using electron cryomicroscopy and angular reconstitution, structures at 20 A resolution were obtained, which, when compared with our earlier reconstruction of "empty" ribosomes, showed densities corresponding to tRNA molecules--at the P and E sites for posttranslocational ribosomes and at the A and P sites for pretranslocational ribosomes. The P-site tRNA lies directly above the bridge connecting the two ribosomal subunits, with the A-site tRNA fitted snugly against it at an angle of approximately 50 degrees, toward the L7/L12 side of the ribosome. The E-site tRNA appears to lie between the side lobe of the 30S subunit and the L1 protuberance.
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Stark
authors.forename: E V
authors.initials: EV
authors.lastname: Orlova
authors.forename: J
authors.initials: J
authors.lastname: Rinke-Appel
authors.forename: N
authors.initials: N
authors.lastname: Jünke
authors.forename: F
authors.initials: F
authors.lastname: Mueller
authors.forename: M
authors.initials: M
authors.lastname: Rodnina
authors.forename: W
authors.initials: W
authors.lastname: Wintermeyer
authors.forename: R
authors.initials: R
authors.lastname: Brimacombe
authors.forename: M
authors.initials: M
authors.lastname: van Heel
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008854:Microscopy, Electron / Q000379:methods*; D008958:Models, Molecular; D011132:Polyribosomes / Q000648:ultrastructure; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000648:ultrastructure*; D012270:Ribosomes / Q000648:ultrastructure*
chemical_list: D012343:RNA, Transfer