The complete amino acid sequence of ribosomal protein S12 from Bacillus stearothermophilus

The amino acid sequence of ribosomal protein S12 from Bacillus stearothermophilus has been completely determined. The sequence data were mainly obtained by manual sequencing of peptides derived from digestion with trypsin, Staphylococcus aureas protease and pepsin. A few overlaps of tryptic peptides were established by DNA sequence analysis of a chromosomal fragment containing the rpsL gene coding for ribosomal protein S12. The protein contains 138 amino acid residues and has an Mr of 15,208. Comparison of this sequence with the sequences of the ribosomal S12 proteins from E. coli as well as from Euglena, tobacco and liverwort chloroplasts shows that 75% of the amino acid residues are identical within the S12 proteins of all four species. Therefore, S12 is the most strongly conserved ribosomal protein known so far.