Involved in correct processing of both the 5' and 3' ends of 23S rRNA precursor. Processes 30S rRNA precursor transcript even in absence of ribonuclease 3 (Rnc); Rnc processes 30S rRNA into smaller rRNA precursors. Cleaves more efficiently on assembled 50S ribosomal subunits. Cleavage is strongly stimulated by ribosomal protein L3 (RplC); 20-30% DMSO can replace RplC, suggesting RplC may alter rRNA conformation. Homodimer. Cells accumulate precursors and mature forms of 23S rRNA with alternative 5' and 3' ends. Defects are more marked during exponential growth. Belongs to the MrnC RNase family.