Amino acid sequence of an active fragment (T2A) of colicin E3

The amino acid sequence of an active fragment (T2A) of colicin E3 composed of 97 amino acid residues was determined. The structures of 6 tryptic peptides obtained from citraconylated T2A were analyzed, mainly by Edman degradation. These tryptic peptides were aligned by examining overlapping peptides obtained from T2A with a Staphylococcal protease. These results, together with sequence analyses of whole T2A from both termini, established the complete amino acid sequence of T2A. The structure and function of colicin E3 are discussed based on the determined primary structure.