2 STREPTOMYCES-LIVIDANS 66 TRANSFER-RNA GENES WITH ANTICODONS CORRESPONDING TO SERINE (AGC) AND ARGININE (CGU) CODONS

From the nucleotide sequence of a 2110-bp Streptomyces lividans 66 DNA fragment two transfer RNA genes were identified: tRNA(Ser) (AGC) and tRNA(Arg) (CGU). These tRNA genes are transcribed from the same DNA st rand and both are preceded by a putative promoter structure. They are separated by an intergenic region of 191 bp. Like most Streptomyces tR NA genes described so far, they do not encode the 3' terminal CCA of m ature tRNAs. Both genes are followed by extensive inverted repeats, wh ich could serve as transcriptional terminator signals. Remarkably, the se hairpin structures share an identical 9 base pair stretch (5'-GAAGC CCCG-3'). Furthermore, the tRNA(Arg) region is followed by two potenti al open reading frames, which are encoded on complementary strands and have 3' overlapping ends. The gene for tRNA(Arg) (CGU) is the first S treptomyces tRNA gene described so far which encodes the translation o f a codon with uridine at the third (wobble) position.