THE COMPLETE PRIMARY STRUCTURE OF RIBOSOMAL-PROTEIN L1 FROM THERMUS-THERMOPHILUS

The primary structure of the 23S rRNA binding ribosomal protein L1 from the 50S ribosomal subunit of Thermus thermophilus ribosomes has been elucidated by direct protein sequencing of selected peptides prepared by enzymatic and chemical cleavage of the intact purified protein. The polypeptide chain contains 228 amino acids and has a calculated molecular mass of 24,694 D. A comparison with the primary structures of the corresponding proteins from Escherichia coli and Bacillus stearothermophilus reveals a sequence homology of 49% and 58%, respectively. With respect to both proteins, L1 from T. thermophilus contains particulary less Ala, Lys, Gin, and Val, whereas its content of Glu, Gly, His, Ile, and Arg is higher. In addition, two fragments obtained by limited proteolysis of the intact, unmodified protein were characterized.