Hybrid 5 S ribosomal RNA encoded by a multicopy plasmid is incorporated into ribosomes of Escherichia coli.

The recombinant plasmid pJR3 delta contains a tandem pair of promoters from rrnA followed by a hybrid 5 S rRNA gene, derived from the two 5 S rRNA genes of the rrnD transcription unit, and a terminator. Escherichia coli cells transformed with this plasmid produce 2-3-times more 5 S rRNA compared to untransformed cells. The growth of cells containing this plasmid is not affected significantly. Although the sequence and the secondary structure of the plasmid-specific 5 S rRNA differ from those of its counterparts (e.g., from 5 S rRNA species encoded by chromosomal genes), it is processed properly and is incorporated into ribosomes.