Two large clusters with thirty-seven transfer RNA genes adjacent to ribosomal RNA gene sets in Bacillus subtilis. Sequence and organization of trrnD and trrnE gene clusters.

Sequences of two large tRNA gene clusters (trrnD and trrnE) in Bacillus subtilis 168 revealed 16 and 21 tRNA genes, respectively, as identified by anticodon assignments. Each cluster contains upstream flanking 23 and 5 S rRNA sequences. The 23-5 S intergenic space in trrnE corresponds exactly to the analogous space in trrnB, which was previously sequenced (Wawrousek, E.F., and Hansen, J.N. (1983) J.Biol. Chem. 258, 291-298). The 5 S rRNA genes in trrnB and trrnE are B. subtilis major species; but trrnD possesses a minor species (Raue, H.A., and Planta, R. J. (1977) Mol. Gen. Genet. 156, 185-193) gene with a putative promoter that may allow differential expression with respect to the upstream rRNA gene set. Most of the tRNA genes are probably expressed as large transcriptional units, except for a LeuTTG tRNA in the trrnD cluster that appears to constitute its own operon with putative promoter and terminator sequences. Although all the amino acids are represented among the tRNA anticodons, there are few repeats of amino acid types within clusters; trrnD with 16 tRNA genes has anticodons corresponding to 15 amino acids. About two-thirds of the tRNA genes encode a 3'-terminal-CCA, and these are intermingled with those that do not, with no apparent pattern.