The Amino Acid Sequence of the A Protein (α Subunit) of the Tryptophan Synthetase of Escherichia coli

The amino acid sequences of two large tryptic peptides of the tryptophan synthetase A protein (ar subunit) of Escherichia coti are presented. These two peptides plus those described previously account for all the known tryptic peptides of the A protein. One of the peptides, the largest obtained from the A protein, was purified by gel filtration and paper chromatography. The other peptide could not be obtained intact in sufficient quantities for sequence analyses, but was isolated as two fragments from tryptic digests of cyanogen bromide-treated protein.