Endoribonuclease that plays a central role in RNA processing and decay. Plays a major role in pre-16S rRNA maturation, probably generating the mature 5'-end, and a minor role in pre-5S and pre-23S rRNA maturation (PubMed:22014150). Probably also processes tRNA (By similarity). 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. Assembles into a homotetramer formed by a dimer of dimers. Essential, it cannot be deleted. Depletion experiments show decreased processing of furA-katG operon mRNA, altered processing of pre-16S rRNA, minor effects on pre-23S rRNA processing. A double rnj-rne depletion mutant has decreased amounts of mature 5S rRNA. Belongs to the RNase E/G family.