Transcription termination in the Escherichia coli ribosomal RNA operon rrnC

The distal portion of the Escherichia coli ribosomal RNA operon rrnC has been analyzed to determine (a) the transcription boundaries of an operon containing rRNA genes distal to rDNA, and (b) the sequence elements which dictate efficient termination of RNA synthesis. I have sequenced a 505-base pair DNA restriction fragment containing the genes which specify 5 S rRNA, TRNA1Asp, and tRNATrp, in that order. Segments of a spacer DNA separate these genes: the 5 S-tRNA1Asp and tRNA1Asp-tRNATrp spacers are 52 and 8 base pairs long, respectively. In vitro transcription of restriction endonuclease fragments containing the distal portion of rrnC indicates that termination of transcription occurs at a locus beginning 28 base pairs after the tRNATrp gene. The rrnC terminator shares several features with many other known sites of transcription termination in E. coli.