FIG. 5.

Primer extension mapping of the mutM transcripts. RNA was isolated from S. mutans T8 cell cultures from mid-log to stationary phase at 1-h intervals. (A) Autoradiograph showing the reverse transcripts generated from the mutM primer. The nucleotides at the 5′ ends of the four smaller transcripts are labeled on the right (CCTT). These four nucleotides correspond to the nucleotides at the lower part of the proposed stem-loop structure in the RNA (indicated by the arrows in panel C). (B) With prolonged electrophoresis, the upper band on the autoradiograph was resolved and was determined to correspond to a transcript initiated at the same G residue as that of the mutA transcript. (C) Proposed secondary structure of RNA in the mutA-mutM intergenic region. The Shine-Dalgarno sequence and the translation start codon for MutM are shown by bold letters. The secondary structure was generated by using the RNA Fold program (Genetics Computer Group). See the legend to Fig. 3A for an explanation of the lane labels.