COMPARISON OF FUNCTIONAL PEPTIDE ENCODED IN THE ESCHERICHIA-COLI 23S RIBOSOMAL-RNA WITH OTHER PEPTIDES INVOLVED IN CIS-REGULATION OF TRANSLATION

A new approach for studying functional rRNA fragments has been develop ed based on using a plasmid library expressing random fragments of rRN A. A 34 nucleotide long fragment of Escherichia coli 238 rRNA has been identified that renders cells resistant to erythromycin, when express ed in vivo. The rRNA fragment contains a five codon long open reading frame, initiating at GUG and terminating at UAA, with a Shine-Dalgarno sequence located at an appropriate distance from the initiator codon. Translation of this mini-gene is required for the observed erythromyc in resistance. Experiments with in vitro translated, or synthetic, pep tide indicate the ribosome as a likely target for the action of the id entified rRNA-encoded peptide, which apparently remains associated wit h the ribosome after completion of its translation. The known properti es of the rRNA-encoded peptide are compared with information about oth er functionally active short peptides that can be involved in regulati on of translation.