Hyperaccurate and Error-Prone Ribosomes Exploit Distinct Mechanisms during tRNA Selection

• Published in: Molecular cell Vol. 39; no. 1; pp. 110 - 120
• Main Authors: Zaher, Hani S., Green, Rachel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09-07-2010
• Subjects: Codon - genetics; Enzyme Activation; Escherichia coli; Escherichia coli - metabolism; GTP Phosphohydrolases - metabolism; Kinetics; Mutation; Mutation - genetics; Peptides - metabolism; Phenotype; Protein Structure, Secondary; Ribosome Subunits, Small, Bacterial - chemistry; Ribosome Subunits, Small, Bacterial - metabolism; Ribosomes - metabolism; RNA; RNA, Transfer - genetics; RNA, Transfer - metabolism; RNA
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2010.06.009

Escherichia coli strains displaying hyperaccurate (restrictive) and ribosomal ambiguity (ram) phenotypes have long been associated with alterations in rpsL and rpsD/rpsE, respectively. Crystallographic evidence shows the ribosomal proteins S12 and S4/S5 (corresponding to these genes) to be located in separate regions of the small ribosomal subunit that are important for domain closure thought to take place during tRNA selection. Mechanistically, the process of tRNA selection is separated into two distinct phases, initial selection and proofreading. Here, we explore the effects of mutations in rpsL and rpsD on these steps. Surprisingly, both restrictive and ram ribosomes primarily affect tRNA selection through alteration of the off rates of the near-cognate tRNA species but during distinct phases of the overall process (proofreading and initial selection, respectively). These observations suggest that closure interfaces (S12/h27/h44 versus S4/S5) in two distinct regions of the small ribosomal subunit function independently to promote high-fidelity tRNA selection.
► The rpsD12 ram mutation affects only the initial phase of tRNA selection ► The rpsL141 restrictive mutation affects only the proofreading phase ► Neither mutation affects the rate of peptide release