Endoribonuclease that plays a central role in rRNA and tRNA processing and mRNA decay. Has been shown to act on 9S rRNA (the precursor of 5S rRNA). Endonucleolytic cleavage of single-stranded RNA in A- and U-rich regions. Binds 1 Mg(2+) ion per subunit. Binds 2 Zn(2+) ions per homotetramer. Zinc ions are bound between subunits. May form homodimers or higher order multimers. Interacts with polynucleotide phosphorylase (PNPase, pnp) via the C4 Arg-rich motif (residues 670-678) (PubMed:24563514). A homotetramer formed by a dimer of dimers (By similarity). Belongs to the RNase E/G family.