The Amino Acid Sequence of Streptomyces griseus Trypsin. II The Tryptic Peptides
Streptomyces griseus trypsin (S.G.T.) isolated from pronase was reduced, aminoethylated, and digested with trypsin. The soluble peptides were recovered and the insoluble residue redigested with chymotrypsin. Following recovery of the soluble fraction, the insoluble portion was in turn digested with α-lytic protease of Myxobacter 495. The three groups of soluble peptides were separately subjected to ion-exchange chromatography on the Technicon peptide analyzer and to final purification by high-voltage paper electrophoresis. Sequence analysis by the dansyl-Edman procedure provided unique sequences from the soluble tryptic peptides accounting for 65% of the S.G.T. molecule. Peptides obtained from the redigests of the insoluble residues accounted for an additional 20%.Tryptic digestion of dansylated S.G.T. yielded a unique α-NH2 dansylated peptide whose composition showed it to be the same as the NH2-terminal sequence previously postulated for this enzyme. The tryptic peptides isolated in this work have provided overlaps for many of the previously sequenced peptic peptides. Three continuous sequences of 49, 36, and 28 residues have been elucidated.Evidence has also been obtained that the NH2-terminal valine residue was, to a limited extent, aminoethylated during reaction of the reduced protein with ethylenimine.