|| This family is specific for proteins that encode both the L25 and CTC domains. This protein varies in length; most bacteria encode both the L25 and CTC domains. However a number of bacteria, including some Gammaproteobacteria, Cyanobacteria and at least one Betaproteobacteria have only the L25 domain (see MF_01336), while A. aeolicus only has the CTC domain (and cannot bind 5S rRNA). The function of the CTC domain is unknown. In at least some cases RL25 is dispensible for translation; in B. subtilis this protein is only expressed in vegetatively growing cells. L25 is missing from some Bacillus, Cyanobacteria and Lactobacillus. The equivalent of the highly conserved Asp-87 in Thermus thermophilus (AC P56930) is altered in the Enterococcus and Cyanobacterial genera. There are compensatory changes in the 5S rRNA that are thought to alter its secondary structure and thus permit binding of the protein to rRNA, see: PubMed=15718233; DOI=10.1074/jbc.M413596200; Gongadze G.M., Korepanov A.P., Stolboushkina E.A., Zelinskaya N.V., Korobeinikova A.V., Ruzanov M.V., Eliseev B.D., Nikonov O.S., Nikonov S.V., Garber M.B., Lim V.I.; "The crucial role of conserved intermolecular H-bonds inaccessible to the solvent in formation and stabilization of the TL5.5 SrRNA complex."; J. Biol. Chem. 280:16151-16156(2005).