FIG. 3.
Reverse transcriptase mapping of the transcriptional start site of the ptb gene in B. subtilis 168 grown in the presence (lane A) or absence (lane B) of 20 mM isoleucine. The positions of the cDNA-extended fragments identified with oligonucleotide O1 were compared with those obtained by sequencing of an M13 recombinant phage containing the promoter region with the same oligonucleotide used as a primer (lanes at left, TCGA, respectively, from left to right). Transcriptional start sites are indicated by the asterisks.