An unlinked 5 S ribosomal RNA gene in the archaebacterium, Thermococcus celer

We have determined the nucleotide sequence of an unlinked 5 S rRNA gene region from a thermophilic archaebacterium, Thermococcus celer. This 5 S rRNA gene is flanked by a single tRNA(Asp) sequence and appears to be transcribed as part of a very short operon consisting of only two gene sequences. Comparative studies indicate features in the 5' and 3' flanking sequences, which bear similarity with promoter and termination signals in eubacteria, but also reflect unusual features found in at least some archaebacteria. The evolution of this unlinked operon and the unusual features are discussed.