Partial amino-acid sequence of the epidermal growth-factor-binding protein

The partial amino acid sequence of the epidermal growth-factor-binding protein was determined. Residues in 108 unique positions, corresponding to 45% of the molecule, were identified. The protein is a serine protease, closely related to the nerve growth factor gamma subunit. It is suggested that the epidermal growth-factor-binding protein, like other serine protease, is synthesized as a single polypeptide chain which undergoes limited endoproteolysis. The isolated material also contained minor amounts of a second serine protease. This protease is closely related to the epidermal growth-factor-binding protein, differing from it in 7 out of the 45 amino acid positions available for comparison. The latter protease may be identical to the previously described protease A.