L25 is a single-domain protein, homologous to the N-terminal domain of TL5 and CTC. CTC is a known stress protein, and proteins of this family are believed to have two functions, acting as both ribosomal and stress proteins. In Escherichia coli, cells deleted for L25 were found to be viable; however, these cells grew slowly and had impaired protein synthesis capability. In Bacillus subtilis, CTC is induced under stress conditions and located in the ribosome; it has been proposed that CTC may be necessary for accurate translation under stress conditions. Ribosomal_L25_TL5_CTC is mostly found in bacteria, with a few exceptions such as plants or stramenopiles. Due to its limited taxonomic diversity and the viability of cells deleted for L25, this protein is not believed to be necessary for ribosomal assembly. Eukaryotes contain a protein called L25, which is not homologous to bacterial L25, but rather to bacterial L23.
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