Conservation of primary structure of the pyridoxyl peptide of Escherichia coli and Serratia marcescens tryptophan synthase beta2 protein.

Two labeled peptides were recovered from tryptic digests of the NaB3H4-reduced, performic acid-oxidized beta2 protein of Serratia marcescens tryptophan synthase. These two pyridoxyl peptides were identical except for the presence or absence of an NH2-terminal arginyl residue. Tryptic digestion of nonreduced, performic acid-oxidized protein allowed isolation of the peptides that comprise the two halves of the pyridoxyl peptide. The partial primary structure for this region of the protein was shown to be Arg-Glx-Asx-Ler-Leu-His(Gly,Gly,Ala,His)Lys(Pxy)-Thr-Asx-Glx-Val(Leu,Gly,Glx,Ala,Leu,Leu,Ala)Lys. All the data available indicate that the sequence is identical with the homologous region from the Escherichia coli enzyme.