The ribosome's response to codon-anticodon mismatches.

The ribosome is a molecular machine that synthesizes polypeptides from aminoacyl-tRNAs according to the sequence of the mRNA template. Codon reading by the anticodon of tRNA is controlled by a network of ribosome contacts that are specific for each position of the codon-anticodon duplex and involve A-minor RNA interactions. Rapid and accurate tRNA selection is accomplished by switching the conformation of the decoding site between accepting and rejecting mode, regardless of the thermodynamic stability of the respective codon-anticodon complexes or their interactions at the decoding site. The forward reactions are particularly sensitive to mismatches and determine the variations in the extent of misreading of near-cognate codons, both during initial selection and proofreading. This review emphasizes the progress made in understanding the mechanisms that determine recognition and selection of tRNA by the translational machinery.