Gene organization and primary structure of a ribosomal RNA operon from Escherichia coli

Abstract

The primary structure of the Escherichia coli rrnB ribosomal RNA operon has been determined. The sequence contains the genes for 16 S, 23 S and 5 S ribosomal RNAs, the secondary prophage site for phage λ, the transcriptional initiation and termination signals, as well as the spacers separating the various genetic elements. The entire sequence, ultimately derived from a 7508 base-pair BamHI fragment from the transducing phage λrif d18, is compared to homologous regions from other E. coli ribosomal RNA operons so far available. The main structural features of rRNA promoters and processing signals are shown to be conserved; rrnB has, however, two potential transcriptional termination sites, in contrast to rrnC. Comparison of the sequence of λrif d18 with sequences from other isolates of the rrB operon provides direct evidence for structural rearrangements within rRNA operons. Finally, two potential open reading frames for hitherto uncharacterized polypeptide chains have been found in the sequence closely flanking the rrnB operon.