CLONING OF A GENE INVOLVED IN RIBOSOMAL-RNA PRECURSOR PROCESSING AND 23S RIBOSOMAL-RNA CLEAVAGE IN RHODOBACTER-CAPSULATUS

In Rhodobacter capsulatus wild-type strains, the 23S rRNA is cleaved i nto [16S] and [14S] rRNA molecules. Our data show that a region predic ted to form a hairpin-loop structure is removed from the 23S rRNA duri ng this processing step. We have analyzed the processing of rRNA in th e wild type and in the mutant strain Fm65, which does not cleave the 2 3S rRNA. In addition to the lack of 23S rRNA processing, strain Fm65 s hows impeded processing of a larger 5.6-kb rRNA precursor and slow mat uration of 23S and 16S rRNAs from pre-23S and pre-16S rRNA species. Si milar effects have also been described previously for Escherichia coli RNase III mutants. Processing of the 5.6-kb precursor was independent of protein synthesis, while the cleavage of 23S rRNA to generate 16S and 14S rRNA required protein synthesis. We identified a DNA fragment of the wild-type R. capsulatus chromosome that conferred normal proces sing of 5.6-kb rRNA and 23S rRNA when it was expressed in strain Fm65.