An RNase that has 5'-3' exonuclease and possibly endonuclease activity. Involved in maturation of rRNA and in some organisms also mRNA maturation and/or decay (By similarity). Has an overlapping but not completely redundant role with RNase J1 in the decay of mRNA. Binds 1 Zn(2+) ion per subunit. It is not clear if Zn(2+) or Mg(2+) is physiologically important. Homodimer, may be a subunit of the RNA degradosome. Expressed in cells (at protein level). Part of an operon including SpyM3_0658 and probably SpyM3_0659. Essential, it cannot be disrupted. Depletion experiments show is involved in decay of Class I mRNAs (they decay rapidly in exponential phase, are difficult to detect in stationary phase). Involved in an early stage of degradation of Class II mRNAs (more abundant in stationary than exponential phase, show biphasic decay kinetics). Belongs to the metallo-beta-lactamase superfamily. RNA-metabolizing metallo-beta-lactamase-like family. Bacterial RNase J subfamily.