Digests double-stranded RNA formed within single-strand substrates, but not RNA-DNA hybrids. Involved in the processing of rRNA precursors, viral transcripts, some mRNAs and at least 1 tRNA (metY, a minor form of tRNA-init-Met). Cleaves the 30S primary rRNA transcript to yield the immediate precursors to the 16S and 23S rRNAs; cleavage can occur in assembled 30S, 50S and even 70S subunits and is influenced by the presence of ribosomal proteins. The E.coli enzyme does not cleave R.capsulatus rRNA precursor, although R.capsulatus will complement an E.coli disruption, showing substrate recognition is different. Removes the intervening sequences from Salmonella typhimurium rRNA precursor. Complements the pre-crRNA processing defect in an rnc deletion in S.pyogenes strain 370, although this E.coli strain does not have the corresponding CRISPR locus (strain TOP10) (PubMed:23535272). Endonucleolytic cleavage to 5'-phosphomonoester. Divalent metal cations, preferably Mg(2+). While only 1 Mg(2+) is detected by crystallography, other evidence indicates there may be more than 1 metal necessary for catalysis. Binding of the second metal my be promoted by substrate binding. Non-competitively inhibited by 2-hydroxy-4H-isoquinoline-1,3-dione. Activity is down-regulated during cold shock by direct interaction with YmdB. Also down-regulated during entry into stationary phase by an YmdB-independent mechanism. Homodimer. Loosely associated with ribosomes. Expression increases as the growth rate increases. Encoded in the rnc-era-recO operon. Processes the 5' end of its own transcript leading to mRNA instability. Slower than wild-type growth. Transient accumulation of the 30S rRNA precursor occurs; 90% of 16S rRNA is correctly processed while an extended version of 23S rRNA accumulates in the ribosome. Half-life of a number of RNase III processed transcripts increases. In the absence of era and rnc there is a defect in chromosome partitioning. In strain HT115, loss of immunity against a plasmid with homology to CRISPR spacer sequences (PubMed:23535272). Belongs to the ribonuclease III family. The original rnc-105 mutation is described as G44->D but the nucleotide sequence given indicates G44->S (PubMed:3903434). A later paper calls the same mutation G45->K (PubMed:9632264), which alters the residue and mutation.