Pseudomonas putida tryptophan synthetase: partial sequence of the subunit.

There is 50% identity in the sequences of the first 50 residues of the alpha chains of Escherichia coli and Pseudomonas putida. No deletions or additions of residues are found in this region, except for the N-terminal methionine residue which is missing in the polypeptide isolated from P. putida. Most of the residues which differ are chemically dissimilar, and half of them are specified by codons which differ by more than a single base. The two residues known by mutational analysis to be essential for catalysis in E. coli are conserved in P. putida. The potential taxonomic usefulness of information of this sort is analyzed.