The complete primary structure of elongation factor Tu from Escherichia coli has been elucidated. The protein, which is a mixture of two gene products, consists of a single polypeptide chain of 393 residues. After tryptic digestion of S-carboxymethylated protein, 50 tryptic peptides were isolated covering the complete protein chain. Their alignment was established with overlapping peptides obtained by chemical cleavage with cyanogen bromide and subsequent enzymic subdigestion with Staphylococcus aureus protease, chymotrypsin, elastase and thermolysin. Peptides were sequenced by manual dansyl-Edman and direct Edman degradation procedures.
The N-terminal amino acid of EF-Tu is serine and is N-acetylated. The lysine residue at position 56, in the polypeptide chain is partly methylated. The C-terminal residue is a mixture of serine and glycine, and this was the only heterogeneity found in the EF-Tu preparation used in this study.