Interaction of 10Sa RNA with ribosomes in Escherichia coli

10Sa RNA is a bacterial small stable RNA, in which the 5'- and 3'-end sequences are folded into a tRNA-like structure. The RNA accepts alanine in vitro, and interacts with 70S ribosomes in the cells. In this study, we examined the ribosome-binding properties of Escherichia coli 10Sa RNA in vivo, and found that the aminoacylation ability of 10Sa RNA with alanine is necessary for the binding to 70S ribosomes. 10Sa RNA was also found to bind only to 70S monosomes and not to polysomes. Recently, E. coli 10Sa RNA was suggested to be used as mRNA for tag peptides, which were found to attach to the C-termini of truncated peptides synthesized in vivo. The present results are consistent with the 'trans-translation' model, which has been proposed for tag-peptide synthesis.