The structure of the DNA containing the E. coli tRNATry gene

Using the pMB9 recombinant plasmid pMY3, which contains a functional gene for the tRNATry mutant Su+7, the EcoRI fragment containing the tRNATry gene is mapped and oriented with respect to the HindIII site in the tetracycline region of pMB9. Complete HpaII and HaeIII maps of the EcoRI fragment are derived. The Su+7 tRNA gene is placed by hybridization to these fragments, and the tRNA gene is oriented by using the restriction sites for HinfI, TaqI, and HpaII in the tRNA gene itself. A tRNAAsp gene is shown to lie adjacent to tRNATry, and is also placed and oriented in the map. The RI fragment itself originates in a locus adjacent to, and transcribed in the same direction as, the ribosomal RNA genes of phi 80d3. The implications of the structure of the cloned DNA for its previously measured regulatory and tRNA gene activities are discussed. In particular, the effect on the regulation of RNA synthesis is attributable to an E. coli DNA sequence, but cannot be due to the presence of a normal tRNA promoter on the plasmid.