FIGURE 2.
Gel autoradiographs showing the effects of rRNA mutations on methylation at nucleotide 745 by RlmAI. Mutant and wild-type rRNAs were extracted from E. coli strain TA531 that contains an active RlmAI methyltransferase, and were sequenced by reverse transcriptase extension from the mf11 primer. Methylation at the G745 N1 aborts reverse transcription. (A) All four sequencing reactions for the wild-type strain (98% of the rRNA molecules were methylated); for the 752C mutant (14% methylation); and for the 745C mutant (zero methylation). (B) Selected sequencing reactions (horizontal letters above the lanes) from the other mutant rRNA strains discussed in the text (vertical labeling). ΔA, deletion of one of the adenosines between 749 and 753.