Figure 3.

The ΔcsdA 40S particle contains a 23S rRNA precursor. Ribosomal particles from wt and ΔcsdA strains grown at 20°C were purified on two sucrose gradients. RNA extracted from these isolated particles was subjected to northern blot (B) and primer extension (C) analysis. (A) The p23S precursor results from RNase III cleavage of the initial 30S rrn transcript. Compared with mature 23S rRNA (open box), it caries 3 or 7 and 7–9 extra-nucleotides at its 5′ or 3′ ends, respectively [thin lines (26)]. The probes used for northern analysis are indicated by solid bars. (B) Equal amounts of RNA from 30S, 40S, 50S and polysome (P) fractions were separated on a 1% agarose gel, transferred to a nylon membrane and probed with the 5′-end-labeled oligonucleotides shown in (A). Upper panel, probe 1; lower panel, probe 2. Data obtained with probe 3 are not shown. The positions of precursor and mature 23S rRNA are indicated. (C) RNA from 40S, 50S and polysome (P) fractions was analysed by primer extension using a ³³P-end-labelled primer. A sequencing ladder obtained with the same primer is shown (GATC). The 5′ end of mature 23S rRNA (M) and that of the p23S precursor (+3 and +7) are indicated.