A ribosomal protein from Thermus thermophilus is homologous to a general shock protein.

The gene encoding the ribosomal protein from Thermus thermophilus, TL5, which binds to the 5S rRNA, has been cloned and sequenced. The codon usage shows a clear preference for G/C rich codons that is characteristic for many genes in thermophilic bacteria. The deduced amino acid sequence consists of 206 residues. The sequence of TL5 shows a strong similarity to a general shock protein from Bacillus subtilis, named CTC. The protein CTC is homologous in its N-terminal part to the 5S rRNA binding protein, L25, from E coli. An alignment of the TL5, CTC and L25 sequences displays a number of residues that are totally conserved. No clear sequence similarity was found between TL5 and other proteins which are known to bind to 5S rRNA. The evolutionary relationship of a heat shock protein in mesophiles and a ribosomal protein in thermophilic bacteria as well as a possible role of TL5 in the ribosome are discussed.