We Have Treated a Protein with Chymotrypsin (Cleaves at Aromatic

We have treated a protein with chymotrypsin (cleaves at aromatic amino acid residues) and have isolated a polypeptide fragment produced during the chymotryptic digestion. The amino acid composition of the polypeptide was found to be amino acid moles/mole polypeptide lysine (lys) 2 glycine (gly) 1 serine (ser) 1 phenylalanine (phe) 1. The N-terminal amino acid, determined by the dansylation procedure, was serine. Treatment of the polypeptide with trypsin (cleaves at basic amino acid residues) gave two dipeptides plus free phenylalanine What is the amino acid sequence of this polypeptide?

A) ser-gly-lys-phe-lys
B) gly-lys-ser-lys-phe
C) ser-gly-lys-lys-phe
D) phe-lys-gly-ser-lys
E) ser-lys-gly-lys-phe