|| In some bacteria, for example E.coli and B.subtilis, there are paralogous RL31 proteins. In most bacteria with both proteins the protein that corresponds to the other family (RL31, MF_00501, rpmE) is thought to be able to bind zinc, while this member (RL31B, rpmE2) is not able to bind zinc. It has been suggested based on this observation and experiments in B. subtilis that the non-zinc-binding protein will only be made under conditions of zinc-starvation, allowing the cell to economize on the trace metal, see: PubMed=11574053; Makarova K.S., Ponomarev V.A., Koonin E.V.; "Two C or not two C: recurrent disruption of Zn-ribbons, gene duplication, lineage-specific gene loss, and horizontal gene transfer in evolution of bacterial ribosomal proteins."; Genome Biol. 2:RESEARCH 0033-RESEARCH 0033(2001). and PubMed=12904577; DOI=10.1073/pnas.1733691100; Panina E.M., Mironov A.A., Gelfand M.S.; "Comparative genomics of bacterial zinc regulons: enhanced ion transport, pathogenesis, and rearrangement of ribosomal proteins."; Proc. Natl. Acad. Sci. U.S.A. 100:9912-9917(2003).