Digests double-stranded RNA. Involved in the processing of ribosomal RNA precursors and of some mRNAs. Complements an E.coli disruption mutant, but the E.coli enzyme does not cleave R.capsulatus rRNA precursor, showing substrate recognition is different. Probably also processes some mRNAs, and tRNAs when they are encoded in the rRNA operon. Probably processes pre-crRNA and tracrRNA of type II CRISPR loci if present in the organism. Endonucleolytic cleavage to 5'-phosphomonoester. Optimum pH is 7.5 at 32 degrees Celsius. Homodimer. Loss of processing of 23S rRNA. Full complementation requires both lep and rnc genes, suggesting they form an operon. The protein in strain DMS 938 / 37b4 has 5 other sequence differences. In Rhodobacter species, 23S rRNA is further processed to 16S and 14S rRNA species in vivo, probably by RNase III. Belongs to the ribonuclease III family.