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Characteristics of transfer and ribosomal RNAs from Streptomyces rimosus

We recently determined primary structure of seven tRNA genes and one rRNA gene cluster from Streptomycin ramous. Promoter sequences responsible for the expression of these genes were also defined. Analysed tRNA genes code for tRNafMet Two) tRNAGln(two) and tRNA Glu (three). Gln-Glu genes are organised in a cluster. None of these genes encode the CCA end of the mature tRNAs. Characteristics of initiator tRNAsin Streptomyces is C1-U72 unique mismatch in the first base pair of the aminoacyl stem. Furthermore, G53-T61 "unallowed" base pair is present in one tRNAfMet and second tRNAfMet possess very rare G30-T40 base pair. Two tRNAGln(CUG) differ by one bp in the amynoacyl stem and three tRNAGlu (CUC) are identical and very rich in GC content (70, 3%). All five Gln-Glu tRNAs recognise GC rich codons which are preferentially used in Streptomyces genes. Ribosomal RNA genes in S. rimous are clustered in six very similar gene sets, with genes organised in the order 16S- 23S-5S. Primary structure of one rRNA gene set (rrnF) was determined. Three genes in the cluster, separated by short intergenic regions, code for 1529 nt long 16 S rRNA, 3121 nt long 23S rRNA and 120 nt long 5S rRNA. 16S rRNA shows high homology with other known Streptomyces 16S rRNAs, but also contain s highly variable species - specific region (nt 175- 200), 23S rRNA is the longest sequenced prokaryotic 23S rRNA with insertions found mostly in the 5'end of the molecule.

tRNA genes, rRNA genes, promoter, tRNAfMet, tRNAGln, tRNAGlu

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