An RNase that has 5'-3' exonuclease and endonuclease activity, with the exonuclease activity probably being most important in vivo. Involved in maturation of 16S rRNA, rnpB (the RNA component of RNase P) maturation and degradation, and mRNA maturation and/or decay. This subunit probably plays a structural rather than enzymatic role as mutation of its putative active site gives no phenotype, and its deletion is partially complemented by inactive RNase J1. Binds up to 2 Zn(2+) ions per subunit. It is not clear if Zn(2+) or Mg(2+) is physiologically important. Homodimer (By similarity). Component of a possible RNA degradosome complex composed of cshA, eno, pfkA, pnp, rnjA, rnjB, rnpA and rny. Interacts specifically with RNase J1. Very sensitive to temperature and medium changes; slow growth at 37 degrees Celsius on Mueller-Hinton medium, poor growth at 30 degrees Celsius. No growth on other media at 37 degrees Celsius unless supplemented with MgCl(2), nor at 42 or 25 degrees Celsius. Double rnj1-rnj2 mutant grows much slower than either single mutant and only at 37 degrees Celsius. Belongs to the metallo-beta-lactamase superfamily. RNA-metabolizing metallo-beta-lactamase-like family. Bacterial RNase J subfamily. Truncated N-terminus.