GENES ENCODING THE 7S RNA AND TRANSFER RNASER ARE LINKED TO ONE OF THE 2 RIBOSOMAL-RNA OPERONS IN THE GENOME OF THE EXTREMELY THERMOPHILIC ARCHAEBACTERIUM METHANOTHERMUS-FERVIDUS

Analysis of gene structure in the extremely thermophilic archaebacterium, Methanothermus fervidus, has revealed the presence of a cluster of stable RNA-encoding genes arranged 5′-7S RNA-tRNASer-16S rRNA-tRNAAla-23S rRNA-5S rRNA. The genome of M. fervidus contains two rRNA operons but only one operon has the closely linked 7S RNA-encoding gene. The sequences upstream from the two rRNA operons are identical for 206 bp but diverge at the 3′ base of the tRNASer gene. The secondary structures predicted for the M. fervidus 7S, 16S rRNA, tRNAAla and tRNASer have been compared with those of functionally homologous molecules from moderately thermophilic and mesophilic archaebacteria. A consensus secondary structure for archaebacterial 7S RNAs has been developed which incorporates bases and structural features also conserved in eukaryotic signal-recognition-particle RNAs and eubacterial 4.5S RNAs. © 1990.