Amino acid sequences of mouse 2.5S nerve growth factor. I. Isolation and characterization of the soluble tryptic and chymotryptic peptides

The determination of the amino acid sequence of nerve growth factor (NGF), prepared as the 2.5S derivative from mouse submandibular glands, has been initiated. Tryptic digestion of S-carboxymethyl- and S-aminoethyl-NGF, followed by purification and characterization of the resulting peptides, was performed. These peptides accounted for 87 residues in the NGF molecule but contained only 5 of the 6 half-cystinyl residues and were missing the amino-terminal fragment. Digestion of the S-carboxymethyl derivative with chymotrypsin yielded 19 peptides covering 108 unique residues. By combined Edman degradation and carboxypeptidase A and B digestion, 96 of the 108 residues, accounted for by peptides from the three separate digests were placed in sequence.