tRNA maturation in Aquifex aeolicus.

Several tRNAs in the hyperthermophilic bacterium Aquifex aeolicus are encoded in clusters and as part of ribosomal RNA operons, implying the requirement for tRNA processing by ribonuclease P (RNase P). Intriguingly, neither a gene for the RNA nor the protein component of this ubiquitous ribonucleoprotein enzyme has been hitherto identified in the sequenced genome of A. aeolicus, despite extensive data mining. As a result of the present study, primer extension analysis revealed that tRNAs in A. aeolicus possess canonical mature 5' ends; yet we were unable to demonstrate RNase P holoenzyme or RNase P RNA alone activity in A. aeolicus extracts under a variety of reaction conditions utilizing mono- and dimeric ptRNA substrates. Processing of dimeric ptRNA transcripts in extracts of A. aeolicus disclosed at least one endoribonuclease which cleaves in the A/U-rich spacer of the tandem ptRNA, reminiscent of bacterial RNase E-like enzymes.