Characterization of ribosomal frameshift events by protein sequence analysis.

In cell-free protein synthesis studies with RNA from phage MS2 as template, normal Escherichia coli tRNASer3 promotes two base translocation at GCA alanine codons with a resultant shift of ribosomes to the minus one reading frame. Similarly, normal tRNAThr3 promotes two base translocation at CCG proline codons. These conclusions were reached by amino acid sequencing of tryptic peptides or cyanogen bromide fragments that contained the reading frame shift site. It is proposed that these frameshift events occur by a two-base pair interaction between the anticodons of these exceptional tRNAs and the noncognate codons.