FIG. 2.

(A) Determination of the transcription start site of the rho gene. Primer extension analysis was carried out with 50 μg total RNA from exponential-phase cells (P.E.). Primer Rho1 was 5′-end labeled with ³²P, extended with reverse transcriptase to determine the transcription start site (arrowhead), and also used in the sequencing reaction (shown on the left). (B) Nucleotide sequence of the rho regulatory region. The bent arrow indicates the transcription start site and was designated position +1, and the −35/−10 sequences are boxed. C-rich sequences are shaded, the ribosome-binding site is double underlined, and the PstI restriction sites are indicated. The arrows indicate the positions of each oligonucleotide used for primer extension, transcriptional fusions, and RNA gel mobility shift assays.