While neither of the L31 paralogs is essential, this protein does not seem to function as the main L31 protein. Has a higher affinity for 70S ribosomes than the zinc-containing L31 paralog; is able to displace it to varying extents, even under zinc-replete conditions. Part of the 50S ribosomal subunit after the end of exponential growth. Only found in ribosomes after the end of exponential growth. In PubMed:12904577 its expression was predicted to be repressed by the zinc-specific metallo-regulatory protein zur; in PubMed:15049826 it was shown that its expression is indeed repressed by zur. Belongs to the bacterial ribosomal protein bL31 family. Type B subfamily.