title: Helix 69 is key for uniformity during substrate selection on the ribosome.
abstract: Structural studies of ribosome complexes with bound tRNAs and release factors show considerable contacts between these factors and helix 69 (H69) of 23 S rRNA. Although biochemical and genetic studies have provided some general insights into the role of H69 in tRNA and RF selection, a detailed understanding of these contributions remains elusive. Here, we present a pre- steady-state kinetic analysis establishing that two distinct regions of H69 make critical contributions to substrate selection. The loop of H69 (A1913) forms contacts necessary for the efficient accommodation of a subset of natural tRNA species, whereas the base of the stem (G1922) is specifically critical for UGA codon recognition by the class 1 release factor RF2. These data define a broad and critical role for this centrally located intersubunit helix (H69) in accurate and efficient substrate recognition by the ribosome.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Rodrigo F
authors.initials: RF
authors.lastname: Ortiz-Meoz
authors.forename: Rachel
authors.initials: R
authors.lastname: Green
mesh_terms: D018388:Codon, Terminator / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D009690:Nucleic Acid Conformation; D010454:Peptide Termination Factors / Q000737:chemistry / Q000378:metabolism; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; C489006:prfB protein, E coli; D012343:RNA, Transfer