ESCHERICHIA-COLI B LACKS ONE OF THE 2 INITIATOR TRANSFER-RNA SPECIES PRESENT IN ESCHERICHIA-COLI K-12

We show that the metY locus which specifies tRNA2fMet in Escherichia coli K-12 specifies tRNA1fMet in E. coli B. This conclusion is based on results of Southern blot analysis of E. coli B and K-12 DNAs and on polymerase chain reaction amplification, cloning, and sequencing of an approximately 200-bp region of DNA corresponding to the metY loci of E. coli B and E. coli K-12. We also show that the metY locus of E. coli B is transcriptionally active. E. coli strains transformed with the multicopy plasmid vector pUC19 carrying the metY locus of E. coli B overproduce tRNA1fMet in E. coli B and E. coli K-12 in contrast to strains transformed with pUC19 carrying the corresponding locus from E. coli K-12, which overproduce tRNAf2Met.