Figure 1

RNase III cleavage sites in the 5' strand of pre-23 S rRNA. 70 S ribosomes and 50 S subunits were isolated from the RNase III positive (XL-1B) and from RNase III negative (CAG) strain. The 30 S rRNA precursor was transcribed in vitro. Samples were treated with RNase III (+ lanes). Control samples were incubated without the enzyme. RNase III cleavage sites on the 23 S rRNA in the ribosomes or in the naked RNA were determined by a reverse transcriptase primer extension. The sequence of the rrn B operon around the 5' end of 23 S rRNA is shown on lines A, C, G, T. RNase III cleavage sites and the mature 5' end of 23 S rRNA are indicated on the right (-7, -3, and 5' 23S).