FIG. 4.

Identification of the 5′ ends of patS transcripts by primer extension. Total RNA from filaments grown with 17.6 mM NaNO₃ (lane 0) or from filaments collected at 12 and 24 h after nitrogen step-down was hybridized to ³²P-end-labeled primer A (A) or C (B), extended with reverse transcriptase, and analyzed on a 6% polyacrylamide gel. Samples of 30 μg of total RNA (A) and 15 or 100 μg of total RNA (B, lane a or b, respectively) were used. The fragments are labeled to indicate the position of the 5′ end with respect to the patS translation initiation codon shown in Fig. 3A. Lanes T, A, C, and G are dideoxynucleotide sequencing ladders of pAM1035 produced with the corresponding primers A and C.