FIG. 3.

(A) Characterization of hemZ transcriptional unit by Northern blot analyses. RNA was isolated from B. subtilis wild-type strain 1012 grown under aerobic conditions. After electrophoresis in 1.2% denaturing agarose gels and transfer to nylon membranes, hybridization was performed with riboprobes directed against the 5′ end (5′) and 3′ end (3′) of hemZ. We used 5 μg of RNA for the assay shown in lane 5′ and 10 μg of RNA for the assay shown in lane 3′. The positions of RNA size markers are indicated. (B) Mapping of the 5′ end of the hemZ mRNA. Primer extension analyses were carried out with the oligonucleotide hemZ-PEX and 20 μg (lane 1) or 5 μg (lane 2) of RNA prepared from exponentially growing B. subtilis 1012 cells under aerobic conditions. DNA sequencing reactions utilizing the same primer and plasmid phemZPEX were performed in parallel, and the reaction products were separated on the same gel (lanes A, C, G, and T). The mapped 5′ end of hemZ mRNA is denoted by an asterisk.