Nucleotide sequences of tRNA genesin Streptomyces lividans66

Three DNA fragments of S. lividans 66 which hybridize with labeled tRNA were identified and the nucleotide sequences were determined. A 907 bp X7iol-fragment (Ac. no. X52070) contains two copies of a tRNA gene (asnTa and asnTfi; Fig. 1A shows a part of the entire Xhol fragment) which can be folded into the typical cloverleaf structure of mature tRNAs (Fig. 2). Both genes are identical except for two compensating C/G transversions in the aminoacyl stem of asnTfi (C6-G67). Within another DNA fragment of 569 bp (Ac. no. X52072) five tRNA genes were identified which are transcribed in the same direction (Fig. IB). The genes code for tRNA'y(GGC), tRNAy(UGC) and three tRNA(GUC). They are named glyU, cysT, valToc, valT/3, and valTy, respectively. Genes valTa and valTy are identical, whereas valTff deviates in the aminoacyl stem as indicated in Fig. 3. From the DNA sequence of a third DNA fragment (Ac. no. X52073) the gene lysTfor a tRNAy(AAG) was deduced (Fig. 1C). An open reading frame with the codon usage typical for streptomycetes (1) stops at base no. 605 upstream of lysT. Another copy of the tRNA gene (lysU; Ac. no. X52074) is located within a BamHl fragment about 8 kbp upstream. From all tRNA genes shown only gene cysT encodes the CCA 3'-terminus of the mature tRNA. The genes asnT and lysTare followed by inverted repeats of 7 and 15 bp length, resp., which could serve as transcriptional terminator signals.